How do I make my codes efficient? :/

Start by writing code. Move on. After 3months go back swear yourself for shit code. Write better code. Repeat.

Still an apprentice and I don't know how far you are but you should avoid ultra long code classes and use multiple classes with different purposes you can reuse. But this could become really chaotic too so you need to know what classes are, how they work and what OOP is.
I repeat I don't know your programming skills, so if you already knew this, sorry for wasting your time.

Write in assembly language. /s

Many IDEs have code optimization tools, visual studio (especially with resharper), intellij, ..

But for the code itself helps only learning through overflows/experience, i.e a calculator tool taking 8gigs of ram to run and then looking into why it happens.