Most people tend to speak their native language, English, and then claim some kind of third.
Technically I can speak Irish, Dutch and Japanese, just not in a manner that's fluent. If I'm outside any of these countries or near no one who speaks it, I'm a bilingual genius but when I have to contend with it directly I shell up.
A lot of people claim to be bilingual when they're not really, so I guess I get what TS is asking, but I have no idea about GGG personally. I've heard Mc Greagor claiming to speak Irish but it's pretty apparent to me when he speaks it that he's about as fluent as any third-year student trying to scrape a pass in ordinary irish.
Also, English is absolutely fucking everywhere and everyone is told from day 1 to speak it, which leads people into taking it for granted as if the whole thing isn't full of caveats.
I'm actually fluent in German and Croatian. English is my third language. I spoke both German and Croatian as a child. And lived in both language Areas while growing up, so I'm equally fluent. And my English is fluent too, that is a learned skill, with youtube, social media and the internet, and school. Besides that I was bad in school.
With language areas I mean to say German and Croatian are not just spoken there but some countries got their version of those language. As in Austria or former Jugoslawian countries. I'm sort of trying to be not too personal online and obviously failng at it.
Basically Austrian is German with a different accent.
Croatian is the same as Serbian, Bosnian and Montengrian. Macedonian is extremely close. Slovenian is probably extremely close too, never bothered to check it or ran into slovenes. Even Bulgarian is like Croatian / Serbian.
Switz now is kinda different like a funny weird German.
I was sort of like I speak 3 languages and this guy speaks 4, one of them being German, I bet he doesn't really speak it though. I got a buddy in Germany he lives here for probably 8 years and I am being serious when I say he can't say 1 full sentence in German, he literary doesn't speak German at all. At his construction job he is surrounded with his language, so also in private as there are quiet a few jugoslawian bars and people and he never has to learn German.
I think even my uncle was like that he was in Germany a few years and didn't even speak it, that was long ago though.
I bet GG sounds broken in German

. But of course I respect the man. He is a world class fighter, not linguist.