When I use my headphones on my pc they are loud enough, but when I plug them into my phone they are way quieter. I already tried those volume boost apps and none of them worked.
No wonder, there is nothing wrong with your headphone. The headphone does not amplify the signal, you get what the device outputs. Simply a battery powered device has lower power output designed on its audio connector. That is reasonable.
A desktop pc a hi-fi amplifier does not have such restrictions.