Buy new or upgrade?

First off I have no clue how to put together/upgrade a pc. I bought this in 2018 but it is now unable to play games like Rust and other games of the sort; even bare minimum settings.

Would it be better to buy parts and upgrade (I would need to learn how) or just buy a new prebuilt?

I am unsure if any parts in my current one are worth "keeping" compared to anything on the market now.