Is it okay to learn karate for a few years and then go to Sanda?

It's entirely possible. As the saying goes, "there is one martial arts family in the world", and the ways of martial arts attack and defense have something in common. Karate originated from China Wushu, which is very aggressive. Moreover, Sanda is comprehensive, which is a modern saying, not a genre. Sanda is a martial art with practical value formed by combining the strengths of various schools.

Routine is not a problem. Routine is used to memorize some attack skills, and now it is mostly used for performance. Practicing routines has little to do with practicing martial arts. However, this does not mean that routines are worthless, on the contrary, routines have high value. Sanda routines and karate have many similarities. You know, there is no exact genre definition of Sanda.

It's good to practice martial arts and be familiar with the technology of many schools. Bruce Lee studied a variety of martial arts, and finally went to the rough and refined, and founded Jeet Kune Do.

But I suggest you learn Jeet Kune Do, which can help you better understand the essence of martial arts, not just learn simple routines.