you could just pick a bigger case if you haven't ordered it already ^^
ye the 5900x needs either a substantial air cooler or a 240mm+ AIO
the AIO fits in small cases too. if you're set on using that case, it might be easier to go with one of these. I'd rather change the case but if you already got it, adapt
https://www.jimms.fi/fi/Product/List...missarjat?ob=4
but idk much about these various all in ones, you will have to do your own research, or mby headtrauma can help you. the reason why I say do your research is that a few of these, esp as you go cheap, might be known to leak or have pump problems.