.i need some good trainig.

I have been concentrating on this particular skill - making and changing chords - since I started playing about a year ago.  Here's how I did it.  I hope it works for you.  I'm sure there are many other ways.

First thing I did was to find a song I wanted to play that had only three or four open chords. 

Then I looked carefully at the chords and thought about which fingers would go where when I changed between the chords.  I would build a chart of chord changes.  The chart would look something like this

G - C
C - G
G - D
D - G

Then I picked would write out the chords beside the transition notes.  As you get to know the chords, write them from memory and check if you got them correct.  That will help you to remember chord shapes. 

Once I knew what all the transitions were, and planned how each finger was going to travel from one chord to the next, I would practice each chord change many times.  What I did at first was to remove all my fingers from the finger board and make the new chord.  Eventually, I learned that I could leave certain fingers on the fingerboard or just slide them from one string to the next.  But I think at first learning to make the entire chord quickly was best for me. 

I would go through this exercise for each chord change maybe 100 times.  I didn't count, I just did it until it was easier than at first.  Then I would add strumming.  I'd go with just 1/4 note strums while doing the chord changes.  When I didn't stumble too much, I started to sing along.  Once that was better, I would try to get strumming patterns that were more interesting. 

I hope that routine will be useful to you.  Best of luck.

- Zurf