Explain Jesus statement 'If I bear witness of myself my witness is not true' John 5 v31?

Anyone can claim himself to be a god, even you. But to be reliable you need a witness. You can't be witness of yourself, because then your opinion is one-sided. With Jesus it was otherwise

• The Bible was his witness, which means that prophecies were

fulfilled in his life - birth from a virgin, from house of David, in Bethlehem, and about 200 others(i don't exactly remember how much) including crucifixion (with details - especially in Psalm 22 and book of Isaiah), resurrection and any other important event in his life. Also The Father God himself was his witness - on the Tabor mountain together with Elijah and Moses when he told his 12 apostles that He is his beloved Son, and they have to listen to him.