There are a lot things that could have gone wrong and it is hard to say something with 100% confidence without looking at the Analytics and Search Console.
Read this blog to discover what mostly goes wrong when traffic and ranking suddenly starts disappearing, https://www.upreports.com/blog/google-ranking-dropped-dramatically/

Hello, I have been helping small businesses and startups with creative vision and concepts for over 7 years now. I can look at your target audience, product, motivations, and other factors to help craft content that strikes the right chord with them.
Here's a presentation which is the result of my creative vision, https://www.slideshare.net/upreports/growth-hacking-tips-techniques-for-beginners
Skype me (varun23123) to discuss further. Thank you!

Domain advantage will not be passed on to the subdomain. Google will treat the subdomain as a different website.
If you want to pass site juice to the trainer pages, then set it up as normal pages, like:
domainname.com/trainername
domainname.com/trainername

Buying new sites for all trainers will not pass domain juice. I hope this helps. In case of further help with SEO, email me at varun@upreports.com

Hello, growth hacking can be applied to offline businesses and services too. There are a lot of businesses dealing with offline products that have used growth hacking to multiple sales and profits. SquattyPotty is one such brand.

A lot of growth hacks nowadays use digital channels but depending on the product in question, offline mediums can also be explored.

Last year, I created a PPT that perfectly answers your question. Here is the link, https://www.slideshare.net/upreports/growth-hacking-tips-techniques-for-beginners

Give it a read. If you have any queries, let's get on a call or exchange emails, varun@upreports.com. Thank you!

Hello,
Branding is always important, especially when you are growing. There are a lot of ways to grow your brand but I would recommend you to start online. Why? Because that's where people go to research, find local businesses, shop, and meet people.
Internet is where interactions are happening and reputations are being built. So, I would recommend you to take small steps to build your fitness brand's online identity. Not need to pay big money to influencers and PR agencies.

Here's link to a blog I wrote that shares 100 tips and ideas to build a brand online. I'm sure it will come very handy to you, https://www.upreports.com/blog/build-brand-identity-online-100-tips-ideas/
I also run a brand building agency that helps entrepreneurs with online visibility. In case you need further help to automate everything, don't hesitate to reach out. Here's my personal email: varun@upreports.com
Keep growing.

I have seen this happened with employees too. Employees working very closely with some clients take away few clients and start on their own. The risk is true in your case too but if you partner with an agency with a clean record and a reputation to upkeep, this won't happen. Just be thorough in running an online background check.
I run a marketing agency myself and can lend a helping hand. Feel free to email at varun@upreports.com to discuss.
Cheers!

Ok, we have a couple of things that can be handed out and some things that are best taken care of on your own. Below are the details:

Social media campaigns management for Instagram and LinkedIn - A smart social media guy can do this on your behalf by using tools like Buffer. He/she can schedule everything on Buffer and you can give it a look before it goes live.
- Blog posts writing and idea generation - This can be outsourced with ease. A lot of content creation agencies out there that can write blogs on your behalf. 4 blogs per month will be enough for you I think.
- Networking - Easy stuff. Once you outline what kind of people you want to connect with, anyone can do it. I get this done for LinkedIn.
- Speaking at public events - You got to do this one on your own. Someone can help you with the PPT part but rest of the show is you.
- Produce in-person events - This will also be you.

The first 3 things can be best tackled by a small team after it understands your language nuances, goals, and expertise. First month will be a little time consuming but after that, it will be smooth. My team handles the same for some entrepreneurs and businesses. Below are a couple of case studies:
https://www.upreports.com/pdf/social-media-content-case-study-strategy.pdf
https://www.upreports.com/pdf/blog-marketing-examples-upreports.pdf
I hope this helps. Cheers.

Start with a website. A website of 5 pages communicating your portfolio, experience, and passion will strike the right chords.

Secondly, move ahead and streamline your social media. Pick 3 social media platforms that are most relevant for you and churn out the right content from them. There are agencies that can help out with this.

Thirdly, get your interviews published on a couple of sites so that they pop on Google when someone Googles your name. If you can become a contribute to few top media sites, that's simply gold.

These three are ideas on top of my head but there's a lot that can be done to position your personal brand strongly on the internet.

Reach out if need help with anything above mentioned. I know people who can do amazing things.

Cheers!

I won't recommend building on Wordpress for anything big. Security and scalability challenges will be huge. In addition to that, performance is going to drag with Wordpress.
Money is going to change hands on the marketplace and Wordpress is not known for its security. One hack and you will be on your knees.
Scaling might seem easy if you find the right plugins but if you didn't, things will come to a standstill. A lot of customization will mean paying a huge amount for a 'patched-up' solution.
Go for a modern technology. A lot of PHP frameworks will work and the best one right now is Laravel.
If this is a hobby project, go ahead and use Wordpress.
If it is something that you feel strongly about and want to build right, then, go with a better technology.
Drop me an message if you want to connect with a company that can build it right. I don't want to drop links and look spammy. Cheers!

Investors fund businesses that show promise and a handful of bookings wouldn't cut the deal. How are you going about marketing and branding it?

If you have a strong website that offers flawless experience, then, the right marketing strategy can be the game changer to attract the target audience as well as investors. If you can share what you have been doing in the past 6 months, I can list out the ones you are missing out on.

To get out the tight spot, I would recommend that one of you should get a job and the other one continues working on the startup. If you truly believe in the idea and there is no market leader, then, don't shut down.

Look for other sources of raising money. Good luck!