I put 'I am also here' for the translation into English. It rejected it. Can you explain why, please. Thanks.
Well, to me, it suggests bilocation...
You could say the same about 'I am here too'.
'I am also here' seems just as natural in English, to me.
Sometimes in English, annoyingly, ambiguity really can't be avoided!
OK, I guess you're right... added now.
Another new English word for me!! I won't argue, and here's a lingot.
I guess it would work for St.Padre Pio and St Martin de Porres.
What is the difference between też and zbyt?
'też' means 'as well'
'zbyt' means that there is an excess of something (e.g. 'Jest tu nas zbyt dużo' - 'There are too many of us here')
Is it always used in the beginning of the sentence?
No. In fact, it's 'after the subject' here, because you can treat it as "Ja też tu jestem!" Another common option would after a verb: Zrobili też zupę.
What does the "tu" in this sentence mean?
I'm not Polish, so I wouldn't know, but doesn't it seem strange to have a sentence with such an emphasis on the subject and yet keep it implicit?
Answering: no ;)
Sure, "Ja też tu jestem!" sounds perfectly natural to me as well, but the sentence here is also good.