Start with clean nails (take the nailpolish off if you are wearing any), you should do this prosess for a while, so you won't be able to use any colored nailpolish for a week or two! Yes, you will have boring nails for a long time, but it's worth it. You should now use an nail strengthener, (what brand you use is up to you), you can also try a nailpolisher that makes your nail stronger and grow faster. Apply one coat of the nail strengthener everyday for a week, do not remove any, just apply once a day. Then after a week, you remove the polish and take a few days break, so your nails can breathe and relax (2-3 days). Then repeat the prosess for another week. Then after that, vooiiiila, longer and stronger nails, you can now start using colored nail polishes if you want.