system
Given the following post, respond as if you're commenting on Reddit:
human
[Deadpool] Where did Wade Wilson get those swords, and who taught him how to use them?

[movie] They penetrate into concrete and deflect axe blows from a mildly superhuman guy without breaking, so these definitely aren't run-of-the-mill katanas.  And Deadpool is highly proficient with them, but swordsmanship isn't part of any North American special forces training that I'm aware of.  He wasn't carrying the swords when we see him doing mercenary thug work before his diagnosis.
gpt
Good question. Mix bag of answers here. Also makes some assumptions for the movie. 

So historically Deadpool's Katanas are only special because they actually tie into his suit. Utilizing a function of his suit creates an energy field around his Katanas that make them more durable and able to cut through diamond, though not tougher things like adamantium, vibranium, etc. 

Other version have his Katanas being made of carbonadium, another strong metal similar to those listed above. With these versions he made them with a caster that wolverine had thrown away. 

Idk which versions are considered canon nowadays but typically one of these two reasons is why they don't break. 

Deadpool is competent with them because he is actually a master of kenjutsu, a Japanese way of the sword, though where he learned this is spotty in canon again. All versions of him have him with this competency however, it's just when he learned this that is typically unclear. 

Deadpools mutations also make him have faster reflexes and peak human strength. He can also push his muscles past the threshold of what they would be capable of normally though this is with great detriment to his body and requires his healing factor for muscle repair. So he is naturally more coordinated with swords in this way as well. 

As for why he uses them in the movie, or even in general, it usually doesn't go too far past the aesthetic value of looking cool and turning people into a fucking kabob. Deadpool is actually pretty vain in this way and loves looking cool even if he's the only one who appreciates it. 

Going even further than these explanations; as a meta character it's also possible deadpool is aware that he is supposed to use what weapons he uses and that's why he uses them. That's like 16 walls worth of aesthetic value he's not about to pass up. In his movie he is very aware of who he is, the fact that he's in a movie, and his own comic history as revealed at the very beginning when he expresses shock at getting his own movie and having to perform fellatio to an undisclosed crowd favorite. He's been bitching about getting a movie in his comics and in his comics he's aware of the alternate versions of himself, so it makes using the katanas for the sake of keeping his identity on a meta scale viable.