When i use ''has'' ?

may i change all the time, ''be'' for ''is'' and ''are'' ? for example: ''she is watching a movie'' or ''she be watching a movie''

i dont know if make sense this question here

 i would like travel to europe, but dont know where, what the best countries for go with very nice parties?

when i use ''make'' or ''do'' ? for example, what is correct ? ''i will do a cake'' or ''i will make a cake''

the word ''saw'' is the past of see, and a thing ? on portuguese is a thing ''serra'' and the past of see is ''vi'', on spanish is a thing ''sierra'' and the past of see is ''vi''.

what is the difference between 'may' the mouth and 'may' used on next phrase for exemple 'may i go?' write equal ?

How to say on interrogative form the next question... ''all people speak english there''

i'd like to know what the difference between ''also'' and ''too''