Part of me believes in God but part doesn’t. We’re only supposed to worship God but that sounds selfish. And what about Muslims? How do we know our God is real but there’s isn’t ?
Why wouldn't we want to worship the God of the universe, the One and ONLY God who created you and me?! The Lord who died on the cross to take away our sins and rose again on the third day?! <----- And no that isn't a fairy tale, it is and was true.
(If you have a bible I highly encourage you to read Matthew 27:32-56)
Some verses on your third question about the exsistence of God:
"In the beginning was the Word, and the Word was with God, and the Word was God.The same was in the beginning with God.All things were made by him; and without him was not any thing made that was made.In him was life; and the life was the light of men.And the light shineth in darkness; and the darkness comprehended it not."
John 1
"For since the creation of the world His invisible
attributes are clearly seen, being understood by the things that are made,
even His eternal power and Godhead, so that they are without excuse."
Romans 1:20
"But without faith
it is impossible to please
Him, for he who comes to God must believe that He is, and
that He is a rewarder of those who diligently seek Him."
Hebrews 11:6