Hey there @Mag69,
Unfortunately Raichu doesn't learn moves when leveling up after evolving it with a stone, you'll have to visit a move re-learner in order to re-learn some moves for Raichu, by going to the move re-learner in Saffron for 2,000 pokedollars per move, certain TMs you can use on Raichu to give or catching a Pikachu again and leveling it up first with the moves you want for it then evolving. Or for pre-evo moves, you'll have to do the Daycare quest by completing the Egg Move Guide.
Please let me know if you have any questions.