Q.rubber tree plant
I’ve had my rubber tree for almost reimbursed. Before that, my grandmother owned and cared for it for roughly 4 years. Upon comparing my plant to pictures of others, I’ve found that my plant’s main branch is week and does not stand straight or upright. What can I do to strengthen the branch and encourage upward growth?

You may want to prune the plant back to encourage it to produce lower, stronger growth, as described here:
https://www.gardeningknowhow.com/houseplants/rubber-tree/prune-rubber-tree.htm
The plant may also be weakened if it's not getting enough light, and it may bend toward the light if it's always illuminated from one direction only. If this might be a problem, you could try moving it closer to a window or giving it another light source, and rotating the pot periodically.
https://www.gardeningknowhow.com/houseplants/rubber-tree/how-to-care-for-a-rubber-tree-plant.htm