Can I look up the text of my foreign cards on my phone in MTG tournaments?
At Regular REL, you might get permission from the Judge, at any higher REL it is forbidden.

2.12 Electronic Devices
At Competitive and Professional Rules Enforcement Level
during drafting, deck construction, and playing of
matches, players may not use electronic devices capable of taking and
storing notes, communicating with other people, or accessing the
internet (except for taking brief personal calls with the opponent's
permission).
At Regular Rules Enforcement Level, electronic devices are permitted, but players may not use them to access information that contains
substantial strategic advice or information about an opponent's deck.
Device use during a match other than brief personal calls must be
visible to all players. Players wishing to view information privately
on electronic devices during matches must request permission from a
judge.

You may however, call a judge to have them provide you with the oracle text (the official version of the text in English) anytime.