Since mihawk is titled as the strongest swordsman and there is one samurai in the 5 elders team,so does that mean mihawk is stronger than that gorosei?
We don't know because we don't know how strong that Gorosei is or (really) how strong Mihawk is. Mihawk is likely a better swordsman than anyone in One Piece but that doesn't not mean he is stronger than that Gorosei in any other way.
There are several things to note:
- Mihawk being the strongest swordsman is as much of a title as a display of his ability. If there is a character who is a stronger swordsman, it must be that his ability is underestimated or not known to the world at large. Zoro won't be the strongest swordsman until he can somehow be demonstrated as earning that mantel. As it is Mihawk's defining character trait and Zoro's dream, I doubt Oda has some mystery swordsman somewhere who is stronger with a sword.
- Mihawk's title only refers to his ability with a sword. It is notable that Mihawk's only power seems to come from his reputation and swordmanship. He has no known devil fruit, no shown Haki (though he obviously has Armament), no gimmicks, and no crew. I don't think many people would doubt that Shanks is stronger and Shanks uses a sword. Shank's power, however, includes his crew and his insane levels of Conquerors Haki. If Gorosei must be a stronger fighter, he might be stronger for other reasons than swordsmanship. That being said:
- There is no reason to assume the Gorosei members must be all that strong. Maybe he was the strongest but got old. Maybe he was never that strong but got there based on his intelligence.
(Also Whitebeard was the strongest man but Kaido is the strongest beast. Maybe there is a stronger swordswoman somewhere? But that doesn't apply here... probably. Unless that Gorosei is a Celestial so is not to be downplayed to the level of mere "man"."