I thouht 还 ment besides or además(in spanish)， it gives more informatión but let me give you an example
There are clear examples like when you say i play piano, he plays piano to. Here where you have two subjects doing the same thing is obvius that you use 也。
But in the next example I asked my teacher if you could use 还 instead of 也 and she said that if you use 还 it is not right or properly used. ¿is it because you are still talking about things about his studies in both sentences?. She said 还 would not be proper but would not explain clear to me.
Saludos desde España. Málaga. Greetings from Málaga Spain.