Quick answer
The wifi question: Како́й здесь паро́ль от вайфа́я? Charging: заряди́ть телефо́н.
Devices
Online
Doing things
In use
Borrowed but declined
Words like интерне́т and компью́тер take Russian endings: в интерне́те, на компью́тере. Only a few, like метро́ and меню́, refuse to change.
Typical mistakes
в интерне́т
в интерне́те
Being somewhere takes the prepositional, even online.
мой ро́зетка
моя́ ро́зетка
ро́зетка ends in -а and is feminine.
Check yourself
How do you ask for the wifi password?