Looking to upgrade the rear brakes, chainring, and derailleur on my Mongoose Malus. Have done a few mods already including adding a Shimano Megarange 14-34T freewheel. Any advice?

Looking to upgrade the rear brakes, chainring, and derailleur on my Mongoose Malus. Have done a few mods already including adding a Shimano Megarange 14-34T freewheel. Any advice?

by Most-Emergency7883