Ok, so your PSU would be able to support a GPU like the RX 570 or RX 580 as long as you get a model that only requires one 8-pin (or 6+2) connection.
is correct that you could build your own PC that would perform quite a bit better for the same price as the pre-built. If that is an option available to you then we would be happy to help you through that process.
For now I'm going to assume that returning your pre-built PC is not an option, in which case you're just wanting to make the most of what you have. I was going to suggest that you could try overclocking, but it appears
your motherboard is an ASRock A320M which doesn't support it.
If I'm wrong and you have one of the Z390 Pro 4 boards then you'd have more options.
You can always try tweaking your RAM timings to see if you could squeeze out a bit of extra performance there. Since your APU uses regular RAM as its VRAM, memory speed can have a noticeable impact on performance.
If you are on an especially tight budget then I would recommend browsing the used market. Just a quick search on eBay is showing RX 570s as low as $70 or so, and you might be able to find even better deals on older cards. If you could snipe a GTX 960 or an R9 380 or something for $50 it would give you a really nice boost in performance for less than the cost of a new game.
If no GPU upgrade is possible at this time then you can try taking your games below the minimum settings by removing shadows and doing other tweaks to claw back a few FPS. This video
from The LowSpecGamer demonstrates a few tweaks you can do in Apex Legends (you wouldn't need to go quite that drastic though since he's running it on an Athlon 200GE).
EDIT: I am dumb.