Strike Team Delta hold a wealth of knowledge between them. It made them one of SHIELD's strongest teams. What made them the strongest, was sharing that knowledge...
In the early days, Clint taught Natasha how to use a bow and arrows. Her aim was good, she had the strength but her technique was off. A fast learner and a perfectionist; Natasha was almost as good as he was within days of practice.
Natasha taught Clint Russian. His accent was awful and though he knew enough to communicate; it was nowhere near good enough to convince anyone of any cover story involving a Russian heritage. A little under two years later; Clint went deep undercover with the Russian mob and was able to successfully hold his cover until the completion of his mission three months later.
Natasha taught Clint how to double the amount of weapons he could conceal on his body. She taught him Mandarin, Japanese, Iranian and Arabic while helping him improve in French, Spanish, German, Greek and just about every other language he could speak. She taught him how to diffuse a bomb in less than 30 seconds and how to slip a pair of handcuffs. She taught him to hack any security system and never leave a trace.
Clint taught Natasha to use a knife as a projectile weapon efficiently rather than just rely on them in close combat. He taught her to use a sniper rifle and how to pin an opponent three times her weight. Clint taught Natasha to pilot the Shield quinjets and taught her fluency in American Sign Language. He worked long and hard with Natasha to improve her cooperation and teamwork skills, always used to being a lone agent; it didn't take long for her to adjust to working with Clint however it did take a lot of work until she was comfortable working with others.
They each added to the others arsenal of weapons, languages and skill sets. And that didn't stop with their work life...
Natasha taught Clint yoga and Clint taught Natasha poker; which he soon came to regret when she began to beat him every time... She taught him piano and he taught her guitar. Natasha taught Clint how to dance and he taught her a long list of cocktail recipes. Clint took it upon himself to educate Natasha in the difference between Star Wars and Star Trek. While Natasha saw great importance in teaching Clint how to make pirozhki. She taught him to flirt while he educated her in understanding and using sarcasm.
There were things they both knew how to do; ice skating. Natasha was powerful and graceful on the ice while Clint was more power, less grace; but it was an activity they both enjoyed, though enjoyed it all the more for doing it together. This extended far past ice skating, to swimming, diving, climbing, gymnastics and fighting.
The pair worked long, hard hours to improve their partnership, their friendship strengthened as a result and when they made the move into a relationship; it served them well there too. Joining the Avengers brought with it its own challenges, but there was nothing Strike Team Delta couldn't face together.