It has been over 7 months now and they do not reply to my emails and my funds are still locked

it's most likely because you haven't given them the proof of funds(that they deem valid) that they have been asking from you seven months ago. at this point, they have probably deemed the case closed as the gambler failed to provide the documents that they asked from you, that's why they aren't responding to your emails.
I do small tasks like writing, and designing and get crypto for that and I used that money to deposit and play. I don't understand how to provide the proof of funds. Assume you use your signature campaign earnings to gamble and it's not a valid proof of fund for them, then you will forfeit your money to them?
don't get me wrong, I too find their "acceptable documents for proof of funds" a little ridiculous, but then again, those rules are on their ToS and you did agree to it when you registered an account on their gambling site and they expect you to follow it. it is a shitty situation that I think you can't really win.
They show people winning million dollars and they are scamming me for $300. Maybe those promos and social media posts are fake and big fraud is going on.
ALL post on social media about gamblers winning hundreds or thousands and even millions are all real, nothing is fake buddy, I have a close friend who have won close to $500,000 from stake in total since he started playing there, it's been like over 3 years now, he has never had any issue with his account or with his withdrawals being processed, one time, he won over $10,000 and wanted to withdraw, he was asked to kyc which he did, after that, it's been a smooth ride for him for over 3 years now...
Like every other persons have said, mistakes most gamblers make is neglecting or not abiding by the terms and conditions of the casino, if you breach it, they have the right to suspend your account, and you must provide whatever they ask, else, your account won't be restated, this is far different from being scammed.