Major S6

Both anime are about baseball, both main characters are not intelligent however they are excellent at baseball and get stronger as the story progresses. However Major focusses more on the protagonist while diamond no ace goes more in depth into the entire team. 

they have a sport side and romance and the main characters look like them 

Both are sports anime that focus on the psychological struggles of athletes, and the impact on their performance. They also focus on a lot of the hardships that professional athletes had to deal with, such as fan/team pressure 

both main characters have the spirit to figth with the adversities in the training and in the game (ring for ippo) 

Goro and Tokuchi both kick butt in professional baseball, and both shows are amazing. Goro uses more will power and skill, while Tokuchi is kind of like a mind reader and has a very psychological and tactical method of approaching baseball. If you like one show you will like the other (but I suggest watching Major from the very beginning if you want to get the whole story). 

The same type of anime, characters, atmosphere only it's about tennis ! I think 100 of the people who like Major will love PoT! 

Gorou (Major) and Minato (Tsurune) are talented athletes who must overcome the psychological condition that has damaged their sports careers. Sports anime generally do not cover sports psychology issues and when it does it is often quickly introduced and resolved (sometimes in an unhealthy manner) as part of a character arc. Tsurune and Major S6 give proper attention to their main character's psychological conditions and how it affects them and their team. If you are interested in this aspect of Tsurune or Major S6 then you have found another anime to watch. Of course, Major is significant time investment to reach season 6.