Man-O said:
Met a cool girls at a bar through eye-contact followed by cheering to each other ( I was on the other side of the bar). Went over to her and she was open for talk. Learned that she had been a volunteer the same place as I am now and number closed her after telling that she was cool and I'd like to know her more as I had to find my friend (5 mins passed).
Sounds like you guys were just having small talk.
Man-O said:
1.30 AM
Me: "Now you got my number. Man-O

"
5.30 AM
Her: "Hey Man-O. Thanks for the number

Just so you know, I'm not looking for anything else than friendship.

"
2 days later
Me: "Well well, so you don't trust me=

"
1 day after
Her: "It wasn't what I said ;-) ;-P But it is always nice with lear/drawn lines

"'
Other than the fact that she wants to "just be friends," I can't tell if she is trying to subtly say anything else. In fact, I highly doubt she is communicating anything else.
I don't know the full context behind this text though. All I can say is that it was definitely something you did or said that put you in this position.
*Side note: Don't say "well well." You make it sound like you caught her in the act of doing something naughty. Words like "What?" and "Oh" are much more suitable replacement words.
Ex:
The ideal text/what I would text:
"Oh, so you don't trust me?

" <--- This hints that you are capable as being something much more intimate and sensual. Low effort, and sexy as h*ll.
Saying something akin to this:
"Ah, I guess you don't trust me

" <--- means you are defensive about being friend-zoned.
What you said:
"Well well, so you don't trust me=

" <--- means you want to be more than friends but you're just not pushing hard enough to escalate.
Also, you took a really long time to text her back (in terms of meeting her via cold approach. You get more time with social circles since you see the person more often.). Try to be quicker next time so her interest is still captivated by you, otherwise you could end up boring her. This does NOT mean to text her within 30 seconds of getting a message, I just mean that if you get an text back from her, initially, then be sure to take 5 minutes out of the day to text her back.
Man-O said:
So how am I supposed to interpret this? Do I keep gaming or just let myself get fz'ed? What are the reasons for her behaviour? What might I have been missing in the interaction? Help plz.
H*ll no. Keep gaming and don't take any of this. But before I go on...
I don't think you built a connection with her. It sounds like you guys stuck to small talk (which screams friend zone, and you have to get past that).
Read:
https://www.girlschase.com/content/getting-past-small-talk
So yeah, you guys have something in common, but you (probably/should) have stuff in common with your bros, family, coworkers, etc. That just isn't enough to date/get you into a relationship with her.
Be sure to make you're intentions clear by being decisive, concise, direct, and a little bit sexual. That way she knows what she's getting and doesn't have to "draw the line" (and she won't want to if you pull it off right).
EDIT:
I get it now, she's just hesitant to be more than friends with you and doesn't think it would work to have you as a lover/boyfriend. Prove her wrong and persist a little with her. She wants to feel secure, to be understood, and have mutual trust. Fulfill those things and follow that last bit of advice I gave you. And remember, it doesn't always matter what you do so much as how you do it.