I need help I am a noob

I am using blender so i can insert part’s in Roblox and I have a tree and I need to split it in 3 section to import it because 5000 triangles is the top I can use I can’t manage to find on the internet(or I am just an idiot) I don’t now how pleas help!!

Please put that into clear Engilsh so we actually know what you are talking about
For ALL support questions please ALWAYS supply screenshots and supply a demo blend file for review.