I have Ubuntu 18 installed in my computer. I want to installed elementary OS. I kind started liking it. But I have so many apps installed in the Ubuntu installation and I don't want to lose those. So is there any of turning my Ubuntu to elementary OS?
You could, but will be painful and you'll probably lose time and data in the process. And definitively you'll break the system
Is better to save
/home if you don't have it already in a separated mount point and then install elementary OS fresh. Create a list of the apps you use an want that way you can install them later and because you saved
/home you will have all the settings as before
I will comment that I could be give you some pointers on how to do it, but I will not because I find that you'll probably hate elementary and go back to Ubuntu. You deserve the full and proper experience