I don't understand anything from this game

Hello there !

I recently started playing Warframe and I don't know what or how to do things ! I can't do missions because something, I can't upgrade things because I don't have upgrades. When I'm trying to do missions I get stuck up with 100 other players who run in every direction and do stuff and i don't do jack shit.

I just went to Cetus and tried a Bounty Mission. It directed me outside the town and from there 1000m, but the party I was thrown into was already there ... WTF ? I ran in that direction, then the quest was over, then another quest popped up and it was another 1200m in the other direction and again the party members were already there... What the actuall FUCK ? I can't seem to understand anything from this game...

Why do i have to do quests in party ? Let me do them alone. Why can't I unlock quests ? I am lvl 15 and I stuck on earth because I don't know !

Please help me ! It seems like an awesome game but I really don't know how the fuck to play. I am seriously pissed, angry and feel like I'm mentally retarded.