This is unfortunately pretty common when a store first goes live bots scrape new sites and send these is this store open or grow your business spam messages through your contact form.
A few things that usually help
Enable reCAPTCHA on contact forms (sounds like you’ve done this — keep it on).
Use a spam filter app (e.g. Shop Protector, Hulk Form Builder with spam protection).
Add keyword filters in your email client (filter out messages with grow your business etc.).
If it’s overwhelming, you can replace the contact form with a direct email link, or use a third party form app with stronger spam protection.
It usually calms down after the site’s been live for a while, but spam never fully goes away filters and apps are the best way to manage it.
I use BM Country Blocker to only allow countries that I sell to to visit my website. I also have it set to block bots and any VPN/Tor connections. I have to say it helped a lot.