My question would be: does he obviously hiding a lot of earnings from me in day trading, that he would do from Mars to December? Or is he legit to say he is just waiting all this time the good time to sell BTC when it will be a good time(with a new laptop just for crypto that he bought, not a expensive one, but anyway)
That's not something we would know.
What I can tell you is that you should have came to an agreement at the beginning and stuck to it. If it is to "split the profit" then you should have clarified how you are going to determine the profit. Is it just the profit on bitcoin sale based on "price at the time of sell - price at the time you lent the money", then you have no case in complaining what he is doing with the money! But then why wouldn't you just buy bitcoin yourself?!!
Otherwise if the initial agreement was on ANY profit made with that money then you should have thought about a way to monitor what he is doing, a partnership for example where you are fully involved in all the actions instead of just sitting back and waiting for him to get back to you at some point in the future.
It is not too late to "fix" the agreement either. If he claims he has bitcoin and doesn't do anything with it then ask him to show you the address holding those coins and
sign a message from it. That way you can see the coins and whether they move or not and you are sure he actually owns those coins and didn't just show you a random address.