Fhyujk

In my story a group of people (around 18-20 years old) get superpowers but only slight ones and invulnerability is not one (e.g. percieving time slower and breathing underwater) and only a couple so far have ways to avoid being shot.

Their enemies will be professional SWAT style "operators" with small arms only (MP7s, MP5s, Five-Sevens) so not immensely powerful but accurate and high fire rate.

So what I'm wondering is are there realistic ways to keep the characters alive other than giving these professionals terrible aim or making the characters really lucky?

E.g. what sort of walls would make the shots/enemies non lethal.

You can make it so that one of them has an ability to slightly distort the perception of the SWAT causing them to have a high chance of missing even though they are highly trained.

Don't get caught.

The SWAT team can't shoot them when they don't know where they are or when they manage to flee before the SWAT arrives.

Besides generally being smart and careful about how to travel and how to conceal communication, it might be useful to have some superpowers which allow them to spy on their opponents to find out what they know and what they are up to.

Kevlar vests? Those can stop small caliber bullets relatively easily, leaving bruises beneath them, but nothing lethal. You can buy those over ebay for as little as $50, and they can be concealable, requiring a simple hoodie to cover any bumps. Of course, they can only take so many bullets before they get knackered, so you'd have to get new ones every now and then (the best would be to get a new one even if you were shot just once, as there's always a chance another shot might land in the same spot and might pierce the vest.) But being relatively cheap, I don't think that would be a problem for a group with superpowers.

I'll presume since you didn't list the superpowers, and you specifically describe them as "only slight," they're not going to decide this outcome, but perhaps give them an edge in certain situations. So by-and-large we're mostly dealing with "normal civilians vs a SWAT team."

Even being optimistic this is a stacked, uphill battle.

There's a reason small arms are universally accepted as the most effective way to stop individual combatants, and have been for over a century. Further, these are men and women presumably trained and practiced in the use of small arms, as well as trained and practiced in tactics and teamwork relevant to taking on people.

...with small arms only (MP7s, MP5s, Five-Sevens) so not immensely powerful but accurate and high fire rate.

There's a common misconception (thanks, TV, movies, and video games!) that smaller calibers, such as 9mms, are somehow not that dangerous. This is completely false. You can kill with a 9mm round farther than even trained shooters with a resting firing position can accurately shoot a 9mm. In the linked video he's able to shoot through a sheet of plywood, through a 2x4, and make a clean exit out of it, meaning it has plenty of force. Move to hollow points, and the round will expand, ensuring that the force of the round will be used far more effectively to neutralize the intended target.

So you have trained, coordinated teams with infrastructure and logistics support, with fully automatic weapons that can easily kill a human.

Unless your heroes drastically outnumber the SWAT team, or there is a legal or political reason holding back the SWAT team, an engagement with the SWAT team will not be a win for our heroes.

The only way to win is to not play the SWAT team's game. Never engage with the SWAT team. Run. Hide. Cover their tracks. And if the aforementioned political/legal strategy is an option, use that.

With superpowers listed in the question (and conversation), the team does not stand a chance against a professional "SWAT" team. Use plot devices to save your characters.

With the exception of the immortal one, your young superheroes appear to have nothing that can save them in a gun battle. Of course they can wear bulletproof vests, and that can make a big difference if taking one or two shots, but it won't change the eventual outcome of the altercation. So your team needs a way out.

I suggest that your immortal draws fire to himself, so no other team members are being hit. Then something happens (flash and smoke, maybe some brave ally appearing just in time, etc.), so the "SWAT" team is confused, whereas your team has a way to escape.

This is a well worn plot trope, and you may not like to use it, but unless you somehow upgrade the superpowers, characters would be very likely to get shot and killed.

Perhaps make one of the super-powers a form of intuition. A 'spidey sense', if you will. Such that they can avoid most confrontations, or intuitively know the best route of escape.