I found it !
Hello, and thank you all for the responses !
for those who care:
So, took a week break because of full moon etc. Today was optimal moon only came out at around 01:30, so had lots of time to stargaze.
So after realising you have to remove the dust cap in front of the barel entirely..., no i'm joking ^^ So, this time I almost immediatly saw the grey spot again, witouth losing it after seconds. Yeah what I saw last time was def that. @Waddensky was right about the once you know what to expect, it's easy now. I tried different zoom levels (barlow didn't work tho) trying to see some more detail than a grey eliptic object. (Yes I'm well aware how to use averted vision.) I also got a better sense on field of view sizes and directions (up is down, left is right... and in the telescope it's turned 90 degrees for extra confussion)
Next I went for M13, found it quickly (minus the part where you have to rotate the damn tube and find the correct stars)
It looked similar to the nebula, a grey spot, way bigger and brighter (more white'ish) It was also more round.
I have to say i'm a bit disappointed. No I wasn't expecting high tech satelite imagery or models. But, just a bit more than what i saw. I didn't see any structure except it being eliptic ishhh, sad about these things is that, witouth knowing beforehand what you are looking at, you don't know what it is. Same for M13,
Going from this image I should have seen some dots, (yes I tried changing focus for both objects, the best focus was the same focus used on the stars.)
It looked like this, with it being brighter in the center, I was looking at the correct thing. Yet i didn't see any detail in this neither. No dots, stars just shades of grey.