For some people it's hard to believe that the Father, Son and Holy Spirit is one God. Some believe that the Father is God, and that Jesus was his Son...two entities. However, Jesus tells us many times that they are one.
Here are a few quotes from Jesus, confirming them as 'one':
". . . When a man believes in me, he does not believe in me only, but in the one who sent me. When he looks at me he sees the one who sent me." John 12:44
....I am the way and the truth and the life. No-one comes to the Father except through me. If you really knew me, you would know my Father as well. From now on you do know him and you have seen him." John 14:6
". . . . Anyone who has seen me has seen the Father. How can you say, 'Show us the Father'? Don't you believe that I am in the Father and that the Father is in me? . . . Rather, it is the Father living in me, who is doing his work. John 14:9
"He who hates me hates my Father as well." John 15:23
"When the Counsellor comes, whom I will send to you from the Father, the Spirit of truth who goes out from the "Father, he will testify about me." John 15:26
"I came from the Father and entered the world; now I am leaving the world and going back to the Father." John 16:28
When Jesus rose, on the third day, he said to His disciples, "Peace be with you! As the Father has sent me, I am sending you." And with that, he breathed on them and said, "Receive the Holy Spirit." John 20:21/22
There are many more examples but you get my point. If you struggle to understand or would like to ask any questions then please do so.
Until next time.
God bless!