Secnd, If you mean words we use often while using informal speach it would be "utilisés" not "utilisants" because "utilisants" is not an adjective its the past present tense of the verb "Utiliser (To use) which means you use it more when you tell a story about something that had happened while you or someone was already doing an action.

Ex: En utilisant le grille-pain, je me suis brulé la main. (I burned my hand while using the toaster.) 
 
Here since we dont use it as a verb tense but as an adjective "utilisés" so you could say  
"je ne connais pas trop de mots utilisants utilisés par les jeunes...."

But sorry i live in Canada so the informal french expressions we use with our friends are really different from the one they use in France, i hoped i still helped you
 

Your french is good keep up the good work but you have 2 tiny mistakes that can make you sound like a foreigner if you use them while speaking and writing.

First " j'habite en france il y a déjà 8 ans. " Il y a is an event that happened a while ago, its done and you are talking about it. So here you could say "<em>Je suis arrivé en France il y a 8 ans</em>" (you arrived in France 8 years ago) since your arrival is a past action you can use il y a.
People often use it to whine and say:
"<em>J'y suis allé il y a 5 minutes</em>.." (i went there 5 minutes a go)
"<em>Je l'ai fait il y a 2 minutes!</em>" ( i did it 2 minutes ago)

To express an action you have been doing for quite some time, maybe long of short period of time, you use Depuis

Ex: <em>Je m'entraine depuis Janvier</em>" (i train since January)