I want to start by saying that I really liked the concept of the game and enjoyed playing it!
The feature linked to the action-shooter dominant design make the project very interesting, with so many possibilities.
I would love to see more, like instead of "if you shoot you lose health" i can't stop thinking about "if you miss the shot you lose health" idk
By the way, It needs some more balanced variables, like number of enemies spawn/min, health lost and restored.
Those variables could be adjusted to make the player feel worried and have fast paced thinking, but also give him the possibility to have a short term strategy and rapidly analyze the situation.
Also, I can see a level design optimization by implementing covers (such as in valorant or any other), it could give the player the impression to be good at the game and dont leave because of the frustration given by dying so fast.
Hope these feedbacks help!