What do i need to create or change extensions?

Goodday,

I am using opencart for a couple of years now and my site is getting more and more advanced with bought extensions.
As i get more extensions i get more conflicts between the extensions, which mostly with some help i can solve.
Now i am getting to the part where i have bought some extensions in which i would like to make changed/improvements to my personal needs.
I would like to learn to do this myself, as it is just easier to create things yourself you know in your head what you want but can't explain it clearly to the developers or they don't have the time for it or don't feel the need to make these changed to the extension.
I know some html, a little php and i do understand a little part of how opencart itself works and acts.
At the moment i am reading some php/java/css guide to understand this better, but at about page 150 of the 350 i still don't get how to use this knowledge to improve my opencart website myself.

Can anyone point me to books/ebooks or give general advice of what i will need to learn to being able to make upgrades myself?

Just to explain what i want to do…
At this moment i am starting a sublimation printing business within my 4years live webshop for sticker and decal materials.
For this i need an designer tool, but most (like openTshirts) are for screen printing with t-shirt and apparel as main products.
I do not need these advanced system for pricing, colors etc etc, but i do need more advanced tools than just uploading and positioning an image like the simple extensions do.
For now i have an extension that partially fits my needs, e.g. it does allow my customers to create their own products, resize the uploaded images, add texts scoop layers to front- and background etc.
BUT… i would like to make changes to my needs in ways from changing screen sizes, the way it resizes the standard canvas, the way it outputs an file, create the ability to stack multiple background and choose which will saved in the final print file, create an option to crop images also instead of resizing and many more.
Hiring a developer will cost me thousands of dollars (i have asked some already), and that is not what i want to spend on some software to start off with, but i do want to start of with a great tool to make a good appearance in the competitive world of sublimation printing here in the netherlands.
At the moment maybe even using OpenTshirts would be the best fit to my needs with all the options i like, but the pricing system build inside is meant for screen printing and not for standard full color printing.
If i would use opentshirts i would like to adjust the pricing system in it, to just use the prices in opencart.
But i have no idea where to start to make such changes and would pretty much like to learn this.

Not because i am a cheap son of a dutchman, but more because i have a big interest in learning this as it will make my whole (webshop)life a lot easier and with less frustration if i can change things that others did not yet do.

Thanks in advance,
Greetings Anton

This is a "module template" that helped me out a lot when I was learning how to make modules.

VQMODS are better IMO, and for noobs there is a vqmod generator.

OpenCart is Php, using an MLVC framework. It takes a while to get that concept working, then you need to understand the Libraries and engines that come with a standard OC install.

If you want to learn how it works in order to write your own code, you need to step through the code and understand what each line does. Before long, you'll get the general understanding and will feel comfortable enough to write your own code. Get a good IDE and use something like WAMP and then go crazy. If you get stuck, come back to the forum for help.

- Mel


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