Iphone storage space

Hi guys,
This might be a silly question but does anyone know how to free up space on an iPhone. I buy a new phone every single year because of storage space but I'm trying to avoid that this year because I'm a second-year uni student and I'm saving up money to buy a new laptop. It seems like apple does things on purpose to lure you to buy a new phone: I cam't access my gmails, some calls don't go through, same with messages, if somoene mesaages me on snapchat it will show two days later, when i try to delete photos it won't even work id ahve to restart my phone, I'm so tiredof it hoenstly. Does anyone have any tips on what to do?