Is there some special price on a bundle that allows you to get the 3200G AND the B450m Pro4 BOTH, for 110 Euro, or was that just the price of the motherboard you had listed?
If bang for the buck is the biggest consideration, then this or something similar is probably your best option. This would give you better performance than my i7-6700k, which I currently am using with my RTX 2060 Super, and it works just fine really. So, your bottleneck would probably be no more.
PCPartPicker Part List
CPU: Intel Core i3-10100F 3.6 GHz Quad-Core Processor (€90.89 @ Alza)
Motherboard: ASRock B460M Pro4 Micro ATX LGA1200 Motherboard (€95.70 @ Computeruniverse)
Total: €186.59
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2020-10-31 02:33 CET+0100
However, I REALLY think you could probably eliminate at least some of your lack of performance by adding another 8GB of identical memory to what you have now so that you are operating in dual channel, rather than single channel, because I guarantee you are taking a noticeable performance hit with a single 8GB module running in single channel. I'd probably recommend doing THAT first, or replacing it with a matched set of DIMMs, since there are no guarantees when adding memory that they will play nice together although the probability that they will is very high with 2666mhz and lower speed kits, unlike many of the higher speed kits.
Certainly you are in need of an upgrade at CPU for sure, but your memory configuration is a problem as well and you are leaving some performance on the table that could probably be regained with a rather minimal investment if you can get an identical module to pair up with your existing one.