A better WordPress theme for Auto Spare Parts

Hello all, I have been wrestling with one of the popular auto parts themes for almost a year, to have the site up and running…! I find it very much complex to use this theme.! I would like to know is there any theme that’s very simple and could handle a large amount of vehicle data, I think I have about 70 to 80 thousand rows of vehicle information…(CSV) and that will be distributed according to make, model, etc. So the theme that I use crashes in the admin panel when inserting spare parts…! So I am looking for some simple and straightforward filters to search the vehicles…! What I believe those themes are using WordPress posts tables to store the vehicle data…! it’s better to have separate tables for storing vehicle information…! If anyone is out there to give me hand on this I would really appreciate it…! And definitely, you are a lifesaver. Thank you, (I even do not mind sharing my cp with those who like to help me out)