we do not have any contract or anything written down on paper
This is not just the context, it's part of the problem.
Don't get me wrong, not every favor you do a friend should be documented. But what you're doing now is much more than just a favor.
You need to reevaluate what "friend" means in this context.
As you know I keep most of my funds in cryptocurrencies so often it's not that easy to just get the money out
Not your circus, not your monkeys. Your friend can have his money stuffed under his mattress, in a bank account or invested in cryptocurrency. It doesn't matter. When he needs to pay a bill, that bill needs to be paid. End of story.
However, I do understand that you're lenient towards a friend. Even if you're eventually okay with a delayed payment, there is a dramatic shift in your involvement here.
Currently, you are at your friend's mercy. He pays you when he sees fit (and he clearly isn't bothered to solve this quickly). You have no way of forcing him to pay you, since there is nothing that documents his requirement to pay you.
What you should do, is draft a contractual agreement of the amount to be paid, and by when it should be paid. If your friend needs a delay, and you agree to it, then you're still free to grant him that delay.
But this way, you get a say in things. You need to agree to that delay. If your friend delays too long, or it becomes clear that his delayed payments are unwarranted, then you have the contract to force him to pay.
Don't wait until an issue arises. Document everything in cases an issue arises in the future.
He got very agitated and started asking me if I don't trust him
"Trust me" is not a valid justification. If anything, it is cause for concern if he has nothing to reassure you with other than asking for your blind trust.
and telling me he always keeps his word but I didn't get any unequivocal response.
The fact that he didn't pay you by the agreed upon date proves that he doesn't keep his word. The cause for the delay might not be his fault (e.g. unexpected circumstances), but he still didn't keep his word.
Your friend is essentially arguing that just because he didn't knowingly lie to you, he's not responsible for failing to deliver on something he said he'd deliver.
he told me he gave my phone number to his business manager who will contact me from now on as he is very busy an doesn't have much time, implying that from now on we won't be discussing project details directly
This is a major red flag. He's expanding the business (adding a business manager layer between him and you) yet still not paying the initial costs of the business. He is effectively insulating himself from you and your outstanding bills.
What can I do to make sure I will get paid in a reasonable amount of time. I get the feeling he is very sensitive about this topic. Even though our cooperation isn't going very smoothly I'd prefer to stay on a good terms with him and possibly work together again in the future, but I'm ready to drop the cooperation if necessary.
For the future, always draft a contract.
For the existing payment, you're not guaranteed to get it. If the relationship deteriorates, he's liable to outright refuse any future payment that he's not legally obligated to pay (which is why the contract is so important).
Though I doubt there is much you can do legally, you could consult with a lawyer to see if there is enough documentation (e.g. emails or records) that justify a verbal agreement.
This is just a re-framing of your story. What I say is not objectively more correct than what you say, but I'm showing you a different interpretation of the same story:
You've done work for a startup focused on a recently created business sector which has a tendency to attract people who try their luck at easy money. The company has failed to pay its bills, claiming that its capital is tied up in its own business, but is still asking you to continue work and even increase the work (since you're talking about a higher price).
Repeated requests for payment are dismissed as a lack of trust in the company's financial future. After repeated dismissal of your request for payment you are now redirected to a third party.
It seems to me that your "friend" is treating you like a salaried investor to his company. If it succeeds, you might get your money (if he wants to pay, but it won't be proportional to the financial success achieved). If it fails, you won't see any money.
He has effectively borrowed your money and is intending to either not pay it back (because of bankruptcy, or because he outright refuses and you have no contract to prove anything) or pay it back without interest. This is highly unethical.
If he is genuine and has no ill intentions, you could argue that the outstanding bills can be converted to an investment; which would entitle you to a share of the profits rather than a fixed amount. I doubt he'll ever go for it, and I have my doubts about the viability of his company (given the way he runs it), but if:
- You believe that the company is going to succeed (enough to want to invest in it),
- You don't need the money right now, and
- Your friend is genuinely short on money and well-intentioned
this is a possible way out of the situation. But I'm highly skeptical.