ArthurHTM Hmm, how do I say this... the banana is kinda bad... I think you might be better off doing a complete redesign instead of fixing it.
First: Modules are life. You don't need to, but it's much easier to make effective ships with modules. Separate parts of your ship that can run completely independant. This means having their own crew, power and weapons. There should be no way possible for crew to leave this area, nor for other crew to enter. This way crew will travel minimal distance, optimising firepower and defense.
Example module:
Second: You have no need for shields at the back of the ship if you're never going to show that side to the enemy.
Third: Internal armor is good, if you place it with tact. This is mostly randomly placed. (Or so it seems.)
Fourth: Corridors are a too expensive gap-filler. Use structures, or even better: nothing.
Fifth: Boost thrusters on one side???
Sixth: Put factories directly against weapons for better firepower.
Seventh: Put reactors directly against shields for better defense.
Eighth: Put engine rooms against thrusters, or they are a waste of money, power and crew. They only buff thrusters attached to it.
Nineth: Please read this guide: https://forum.cosmoteer.net/d/7783-cosmoteer-ultimate-ship-design-and-part-guide (Really, it's a how to git gud guide.)
Tenth: I may have sounded a little bit mean in the earlier lines but I don't mean to. The ship sadly is not better than the built-in ships, but that shouldn't discourage you. We all made bad ships when we started out, I for example only started making good ships after I joined this forum. It's just a matter of practise, listening to others and never giving up. You can do this!