Do girls and boys ever masturbate together or teach each other?

First of all do not yell or punish. They will grow out of it.  We all do and they are just exploring their bodies and finding out what feels good. If you make a big deal, they will hide it from you. Let them be themselves and everything will be fine. Maybe just sit down with them and have a conversation in a calm and informative way.  
I use to do sexual things with my sister and  friends but we all grew out of it.  

I have masterbated many times with my girlfriends so much fun

Yes me and some friends used to go in a caravan we had in the yard and chill out one day one of the friends looked in one of the drawers and found some porn mags which I had found earlier. he was so aroused I said shall I show you what I did when I found them, I did and the others asked will you do me to. All of us were hard with our dicks out and I played with each boy in turn ending up with us all playing with each other. it was a great afternoon and we went in there regularly comparing the way we did it.

I want friends i can do it with or we do it to eachother.

Absolutely we do. I learned to finger myself from my best friend when I was 8. We played with each other most days after school. Sleepovers were the best though and sometimes we had other girls too who all participated. By 10 years old we had taught each other how to finger, lick and scissor. Use stuffed animals for pleasure, use electric toothbrushes for amazing orgasms and found a new use for mini cucumbers which we’d put inside each other and use as like dildos.  They were good times and I learned so much from this experiences. 

I think siblings do more often.. me and my sister did it all the time. Started when we were 7 and 8 with just some light rubbing and within a year we were really fingering each other. She’s the older one. Did it till we were 13 and 14.