Trying to figure out Key Signature and Fifths

Hello everyone , new member here so I salute every one of you :)
Okay , well I'm self-taught guitar player (well pretty begginer) so I'm not able to get any education from a musician at the moment , and I'm trying to learn as much as I can in music theory.So far I've got stuck in a one topic that drives me crazy because I just cant understand or cant comprehend it somehow.
What do I do is I'm trying to find the melody in that I hear in my head and I try to figure it out in chord shapes well not in the usual chord shapes we use often.I try to explore in different frets...

So lets say I've found a good sounding chord that I dont even know what it is , this web-site helped me a lot.I find the chord and move on I thought I'm in the key but I'm wrong I'm terrible at it..

So I try to start from scratch I try to go from the first chord I've found but I cant create any progession because I cant find what key I'm in so I cant go from that point.Therefore I dont have any roadmap to create what I want to hear...

Here a very basic idea that I had with a good strumming pattern as I got to know what chord it is by this website.
Here it is ;

I strum this first chord and then add one note to create a melody of course with a strumming pattern I had but its not important here , what important is I want to know what can I do with this and how can I figure out key signature :

D# 9(no 3rd)/C# 6add9(no 5th) D# sus2/A# sus4
---6--- ---6---
---6--- ---6---
---6--- ---8---
---8---- ---8---
---6---- ---6---
---x---- ---x---

D# 7 and then C# sus2/G# sus4
---6--- ---4---
---8--- ---4---
---6--- ---6---
---8---- ---6---
---6---- ---4---
---x---- ---x---

D sus2/A sus4
---5---
---5---
---7---
---7----
---5----
---x----

Okay this is kind of my progression that I had heard in my head but I feel like something wrong and as I dont have any roadmap to figure out the rest of the details what am I supposed to do from now on..What's best way figure out this theory so that I can finally write music properly.My intention is mostly exploring different approach to chords so that I can create melody and a good progression but it comes really hard to me when I try to do that because I dont know exactly to find out key signatures...

Okay lastly I have another question about circle of fifths and sharps and minor chords...So lets say I have D# (kind of obsessed with this chord) , how can I use effectively to find out the key signature from this circle of fifths..

I know its pretty long read but I dont have any musician person that I know to ask , so hopefully someone would explain it very clearly .Thank you in advance.

Check out my Music Theory lesson series. They ought to clear a lot up for you.