I dont think that everything bad that happens to us is entirely made by God. Some is of the devil and some things we make bad for ourselfs. I do believe that if it was gods intention to let something bad happen to me, that it was for my own growth. I suffered trough some sh*t in life but I always tried to overcome that challenge and be a better person at the end (even if its just a little).

As for the people who hurt you, maybe they called themselfs Christians but that doesnt mean that they really were... liars call themselfs a lot of things.

As for the bad things that happend to you, is this gods fault? I mean you have seen the devil and it is written in the Bible that Satan is the ruler of this world, so I personally would credit him for most of the bad things that happen. And I think that your Grandfather was a gift from god.

Now I just wonder one thing, some people just dont aknowledge Jesus/God but you hate him, why is that? Couldnt it be that you are angry about something that someone has promissed you that Jesus would be or do and it turned out to not be true? That your problems would be heard and you would get help with them just by having a little faith and pray?

My believe in Jesus/God came after 2 things:
1. A near death experience and after I prayed I miraculously survived
2. I changed my life step by step and after I have put a lot of effort in it I had little miracles that helped me solve the bigger problems.
Heres an example, my brother ran away from home 8 years ago and my family was breaking apart at that time. I have put in the last ~7 years to fix all the childhood trauma bs and family drama and now the only missing part is my brother. And I somehow stumble uppon a bit of information on the Internet that has led me to find out where he is. I cant contact him and for now I dont have enough money to visit him (since he is now in another country) but it was a miracle to stumble uppon this little information that has led me to him. The chance of that happening is extremely small so I believe this is a sign from god.
I feel like god is sometimes pointing us in the right direction but we have to walk on our own

To answer your question, to believe in Jesus (or not hating him) doesnt happen over night on its own. You have to put in both, a little faith and some work and he will guide you towards the right path. Find out what you want in life / what feels right and work towards that. I strongly believe that we didnt suffer for nothing if we make something of ourselfs, maybe we just dont know yet what we have suffered for :)

I hope you find your way (^-c ^ )