I would prune the horizontal branches back, leaving the main trunk alone. I wouldn't completely remove those horizontal branches right away though. When you prune cut right above a node. A plant should be able to hold itself up, removing some of the weight of those branches may rectify that problem. Or it may be drooping from other reasons, none of my healthy rubber tree plants have ever drooped from their own weight.

Both repotting and pruning are hard on a plant and it takes time to recover from both. I would repot first, give the plant time to settle into the new soil and adjust, then prune. Leaves grow back, roots are less forgiving.

How badly does the plant need repotted? Is it rootbound and needs a bigger home, or are you just giving it fresh soil and back in the same pot?

Maybe just letting it be for now and seeing what some proper care does will surprise you.

Hi Heather, the pot is definitely too small and cannot hold the plant anymore. I will then start with repotting in a bigger pot and in a couple of weeks then prune.

I think in the previous home the plant was never turned and kept receiving light fromt he same direction, that might be the reason why the plant is leaning in one direction, that is also the side where the othere branches are.