Website doesn't fit on mobile screen and mac screen

Hi everyone!
This is a link to my portfolio page:

For some of you, this might look like a nice website. But, if you clicked the link on your mobile phone or from a Mac laptop, it looks like sh*t…

Does anyone know how I can make my website look perfect for all devices (I know all about bootstrap and everything but is there maybe another way to fix the problem more easily? :)))

Thankyou all in advance for trying to help me out x

Hej Tika.
Hoe gaat het?
Looks like you are not using any of Bootstrap’s grid system.
Also, you are using 2 different versions of Bootstrap. (I would not recommend this).

This is the section which explains the grid system (for Bootstrap v4):

For the navigation, I recommend looking at this:
(This is the W3Schools example.) Which changes for mobile view.

You may also find some YouTube videos on Bootstrap Grids.