I am struggling FOR YOU / reason for your stuggling I am struggling WITH Math / what you're having a hard timw with

It depends

You can say both. The two athletes struggled for first place, but only one could achieve it. After the war, there was a struggle for power between competing factions. I struggle with learning French. I struggle with keeping my emotions under control. After having given up smoking, he struggled with his desire to have a cigarette.

I can 'struggle with something', but there can also be a 'struggle for power'.

Struggle with