Giovanni,

It takes 5 rounds for each team to play every other team exactly once. Here is one such collection of rounds. Number the teams 1, 2, 3, 4, 5, 6.

1. 61, 25, 34
2. 62, 13, 25
3. 63, 24, 15
4. 64, 35, 12
5. 65. 14. 23

I suggest using this schedule for the first 5 games for each team, renumbering the teams and using it again for the next 5 days (maybe shuffle the days too). Repeat doing this until each team has played 35 games. The schedule can't be balanced, so for the last 2 games for each team select the matchups you like best.

Good luck!
--Victoria