My understanding is that CSGO is cpu heavy and mostly single threaded.
Your I5-9400F has 6 threads a single thread passmark rating of 2483.
By comparison, a i7-9700F has 8 threads and a single thread rating of 2816.
A decent upgrade.
You may need to update the bios first.
Here is a list of all the processors your motherboard supports:
www.asus.com
The strongest would be a i9-9900k at 3001
9700k would be 2912.
While your motherboard does not support overclocking, the K suffix processors have a higher clock rate at stock.
Clock speed is a valid metric only from the same gen parts.
For example, the 11th gen processors get some 19% better...