I want to a play with a friend in co-op , but he is in the ng++++, and he will not start a new character
Am under the impression that with Dark Souls 2 it doesn't matter in which playthrough you're playing. To play co-op you have to be within a certain number of souls collected and +/- 10 Levels. Apparently you can still be at NG++ and still play together, you can check the Dark Souls 2 Wiki for more detailed info. With that said, I doubt it because by default he must had collected a lot of souls to get there and you will need to farm/grind a lot to get close the summoning threshold.