Much like dramatic scenes, some writers find that writing fight scenes can be difficult sometimes. My main piece of advice is to play out the scene in your head, mainly because it gives you a visual prompt when writing.
Fight scenes should be descriptive and not rushed, because if you rush through it- it loses its importance. Describe not only the actions of the characters but also their thoughts and motives, this way the reader becomes more engaged with the scene.
Motives are very important in fights and you need to think about what is fuelling the fight. A fight that is fuelled by revenge will be more violent than a simple street brawl. The way a person fights depends on their personality but also their motives to fight, so taking that into consideration is important.
Injuries are crucial to think about. If your character is seriously beaten up, they will be injured. Probably badly injured. And with injuries come the illusive recovery time which some writers tend to ignore. If your character breaks their arm, they won't be okay by the next day.
Fight scenes should be full of suspense and mounting tension, making your readers worried about what's going to happen to the characters.
So to summarise, just plan your fight scene in detail, picture it in your head and take into consideration feelings and motives.