Principalmente en mi mente
I would not mind in Spanish is: No me importaria.
Da igual.
en el mente
well you mostly oftenly say it the same but not really
este hombre esta loco!
lo que está en tu mente What is (it) on your mind"En que piensas?" What are you thinking?
En su mayoría no están allá / allí.
¡Estoy aburrido de mi mente!
Depends on what you are talking about, but you can mostly get away with "yo tambien" (me,too)
"soy malo en español, por favor no te molestes"
As well as many native languages - they mostly speak spanish! "sun" in Spanish is "el sol" :D
¿alguna vez pasan por su mente