First of all i don't have any experience on wordpress.. So please forgive my ignorance.. I've found a theme on themeforest. Unfortunately it's a wordpress theme. I want to develop my own admin panel. I don't want to use wordress. Is it possible?
Since a wordpress theme is just a bunch of html/css/js/php files, yes, it is possible. Depending on what language/framework will used backend side, the easiest way would be to extract the html/css/js parts of the theme and than add your own "content-placeholders" which will be used by your own backend.
But: Think twice about doing this. First, there could be a conflict with the license of the theme (depending on what type of license is used by the author of the theme). And more important, second, you should think twice about building your own backend.
For the case this isn't an experiment and you're building a productive website, building you're own backend is a lot of work. Unless you need some special functionalities (or you would like to keep it very slim and basic), I would suggest using a ready made CMS for this - like wordpress.
My opinion: 95% of self-made backends for basic cms features I've seen (and was forced to work with) are very messy and far beyond available open source cms. It seems like many people don't balance the pros and cons of building an own CMS-backend and undervalue the effort to build a state-of-the-art CMS.