Tenho configurações boas no computador mas tenho muita dificuldade em fazer qualquer coisa "complex"

An i5 with 16GB of RAM should be able to handle 1920-by-1080 at 23.976 or 29.97 okay as long as it passes the System Compatabiliy checks (Help > System Compatability Report...).  That is a base system.

As far as render times go, Equiload provides an "AE Test" project for benchmarking our workstations and several users have posted their results (https://vimeo.com/118053656).

When I ran it on a 2010 i5 27-inch iMac, it took 18 minutes and 38 seconds.  By comparison, on a 2020 Apple M1 Mac Mini it took 2 minutes and 29 seconds while a 2019 HP Omen 15-inch i7-10750H CPU @ 2.60GHz with NVIDIA GeForce RTX Max-Q Design 8GB graphics card took 6 minutes and 15 seconds.

For web browsing and watching movies, 256GB is fine.  For video editng and motion graphics, you want your boot drive to be as large as your budget allows for. With a 256GB boot drive, After Effects will have defaulted to setting the Maximum Disk Cache size to 25GB.  For better performance, this should be as large as your budget allow for (realistically, 1TB to 2TB but no less than 512GB).  

Is that SSD the only drive?

How full is it?

What are the hard drives (how many, what kind, what is on each, what capacity, and how full)?

If NVIDIA graphics, make sure to use the latest Studio Driver from NVIDIA (NOT the Game Driver).

What type of media are you editing?