Helloo discolovers, i am getting my fathers disco 1 tdi .. and i wanna make a few changes. Any tips for making it accelerate faster?? Open for some interior tips also (wanna be modern)

hello discolovers, i have a problem. the second gear has a problem , only when the rpm is low i can be kicked in! and when you try to climb a hill and first gear is not enough .. there 's the problem.... any ideas?