I bought a 2001 Isuzu Rodeo 4 wheel drive.

I bought a 2001 Isuzu Rodeo 4 wheel drive automatic last march. It showed a few sign of possible
leakage from low transmission fluid. This is the one underneath. Bought a pump to put it in myself and then the leaking got worse eventually took to mechanic and they put a new seal then about 2 weeks later more leakage hard to drive low fluid again. Parked it after it got so low it could damage something kept putting more fluid in it. Finally, will not go forward still but can go backwards. Found out original prior to purchase the used transmission good one installed was done wrong and it somehow messed up the seal. So now, I am left with a new used car that I can not drive, my only vehicle. What do I do from here? Do I have to replace this new used transmission with another transmission or can this be fixed quickly and financially budgeted or is this another costly endeavor. What is the best solution now. Need help desperate running out time to get it fixed. Thankyou for your answers to this question I really need help with this.