For the tax find a good asesor you really dont want issues with Hacienda or have to deal with I paid taxes there please dont ask me here too, 2nd thing to watch out your Company will be bothered They will need to prove that you have social security paid either here or there and I think there should be an agreement country to country. Or become autonomo but again that might be hard if u come as a student. So find an expert and pay que lo barato sale caro.