I don't know if you like risk or not, but if you really don't have any other way out to get big capital for trading then you might be able to make a loan to the bank, but you have to remember the risks and consequences if you can't afford to pay the debt. but if you want to try then try to collect little by little (profit you can) maybe you can do.
It doesn't have to be a big fund, it's best to have a fund that is ultimately capable of making a big one. Simply you manage the funds you have without having to borrow a bank. That will make you have a big burden. Because the risk of trading is quite large, you can lose at any time. If you lose you cannot return your loan funds.
Perhaps indeed everyone has various ways. But I feel uneasy if I trade using borrowed funds. I believe there is a burden in trading and it has a negative impact on trading results. But there are also those who learn and are proficient then do debt to increase capital and they succeed as well. Remember you must be an expert in using small funds before you use large funds.