How do I restore health to units for galactic battl

me neither..

Healer characters may be what you need.

The challenge of Galactic War is to do all the nodes in a row. If you have a limited roster, you need to manage your health (and perhaps cool downs), for better performance in the next node, as the status of your characters carry over.

You can reset progress and characters once daily.

A lot of teams can heal themselves, not so much at lower levels though.  These teams would do better at Galatic War.  Phoenix was a good example of a team that can heal up.  I guess Mon Mothma and OG Imperial Troopers,  OG Bad Batch, OG Night Sisters are others that would also do this.  I'm unsure how developed they'd have to be for that to kick in to a degree where they'd heal right back up for the next match though.

I have an alt account at Level 58 and so I am intimately aware of the struggles and successes you can have in Galactic War when your roster choices are highly constrained. 

Phoenix survives, but doesn't have anywhere near the offense necessary to punch through other teams with passive healing. You'll struggle against other Phx teams, KRU, and maybe some other teams, but that's who you'll see most at low level. 

Bastila-led Jedi are excellent, and the right team comp will have more offence than Phoenix, enabling you to bash through many teams you wouldn't otherwise be able to finish off. Some comps will struggle against Kanan in particular. He self heals on debuffs and some of the best offensive Jedi will drop debuffs frequently. JKA will help you here bc of healing immunity. Or you can try a full-offence team. I generally bring in Obi-Wan Kenobi or a healer as my last toon in. You mostly won't need healers since most of the enemy damage should be whittling down your bonus protection and you should be killing things before they have a chance to kill a single Jedi. Again, as long as you don't run across nasty passive healing, this is the team to use for as many nodes as you can. Great stuff. Super longevity.

A mix of Empire & First Order seems to do well, but it doesn't have healing, so you can only use it a few times. Attack everything you can with Bastila-Jedi (max her leadership), and when you hit a team you're struggling against because of healing - especially Phoenix if your JKA isn't ready for prime time - Throw in your FO/Emp squad. Ideal comp is KRU (Lead), Moff Gideon, Dark Trooper + 2 more First Order. Dark Trooper is your big hitter here, and so long as he doesn't die, the way his unique works he will heal to 4 stacks at the beginning of every single battle. KRU is also very hard to kill unless the enemy has healing immunity, so the main risks here are that the enemy gets around your KRU taunt and kills off Moff Gideon or your FO toons. Obviously Dark Trooper dying is super bad, but it's also unlikely. 

Try to keep your squads a few levels behind your character level: having 4x level 50 squads is much better than 1x level 55 and 3x level 20. 

I also use a NightSister squad, and I use a different squad on each node 1-4 while the enemies are still easy. This allows those squads to finish with Turn Meter they can use to get a jump on harder opponents later. Then from node 5-12, with one or 2 exceptions, I'm just using Bastila-Jedi. 

Hope that helps! 

I know it now.  The only way is to reset the galaxy war and then all characters will be available.