quicktime doesnt have enough space to screen record why?

i am trying to make a screen recording but QuickTime keeps saying that it could not continue and that i must delete some videos/pictures to continue. i have already deleted many and it still says the same thing. please help me i want this to get fixed ASAP...also if you know of any free screen recorders i can use instead post them below. please don't post trial or any of that. i need the real deal for free. thank you for reading and hopefully helping.