I've been grinding leetcode for an interview in about less than a month too. Similar to your situation (not familiar with trees, graphs, etc.). But have been getting the hang of the easy/medium problems thanks to resources on Youtube, etc. There's sites that show you common patterns and commonly asked questions:

https://neetcode.io (My go to)

https://www.techinterviewhandbook.org/grind75

https://seanprashad.com/leetcode-patterns/

If you want a study partner, I would be down. Best of luck