Tintin rule

Tintin is still male-presenting in those, so we could assume that Transtin is older, meaning she is at least older than 18.

Hergé actually never mentions his age explicitly, he said he'd guess him as being 14/15, but he later said he thought of him as about 17.

In the movie when Tintin is waving with his passport, it says he's born in 1926. Following that Tintin starts with a visit to the USSR. Stalin, Lenin, and Trotsky are mentioned in unison, as well the Red Army; so it must have been after 1918 in where the latter was founded; and before the summer of 1941, when Trotsky died. Plus fours were also commonly worn after 17 years of age, when they then replaced the knickerboxer; and Tintin wears them during most albums.

Following that, Tintin's adventures would start in 1941 preceding Trotsky's death, and the Congo adventure occurs preceding Congolese independence. The moon flight is also mentioned; and in the last album, Tintin no longer wears a plus four, which fell out of fashion (outside of golfing and niche stuff) in the 1970s.

The story of Flight 714 has a Concorde-like aeroplane, which flew for the first time in 1969.

So in a nutshell, Tintin's adventures would've occured between 1941 and the 1970s. At the end of the adventures, he then would've been 44 years old.

If we don't take the passport in the movie as canon too, but take Hergé's word only, then an indicator could be the Holodomor which occurred in 1932-33; Tintin is mentioned as encountering food problems.

But the story about travelling to the Soviet Union came out in 1930, and so a more likely indicator is the famine of 1922-23. If Tintin is indeed 17, this would place him as being born in about 1906, maybe 1907 - Hergé's birth year. That would make Tintin currently 118 years old, meaning he most likely died in the 1980s or 1990s; and his adventures would've ended when he was 63.

Wdym 15 doesnt he live in his own appartement and has a Job as a reporter? Also he travels the world like he is loaded.

I didn't expect that since he/she is literally depicted with a gun in their hands lol. I also think the piece of art in question here is not Hergé OC but an adaption by an artist called lianmilanesa.