Just had my 1st LD using WILD technique 
Flied out my windows doing acrobatic things etc. But all of a sudden the dream reverted back into a non-lucid dream 
I don’t why and how it happened. I didn’t even notice that I became non-lucid.
Can someone give me an advice or tips? 
Short (And Most Appropriate) Answer: Do a search of the forum. You are NOT the first to have this question and will NOT be the last. Many many many people have asked this question (including myself) and their exists many many many solutions out there so forming a new topic to ask an old question merely clutters the forum.
Long Answer: I’ve read that doing things like repeating a mantra inside a dream or calming yourself and staying calm can help preserve the lucid time. You have to be watch your emotions for sure inside a dream when your lucid. In my first LD I got so excited it woke me up. In the middle of the night. If you get too excited you could break lucidity.
Also (more relevant to your case) paying attention to your surroundings and keeping focus is very important. If you go off on a fancy (as I’ve done once before as well 
) you will slowly lose lucidity. You either have to get a lot of experience in LDs so that you can maintain awareness or you have to maintain focus and keep the fact that you are dreaming present in your mind. (Preferably you’d do both until staying in an LD became so natural you wouldn’t have to try anymore.)
Again, (as I might have said a little rudely in the first answer 
sorry) search the forums. There is a ton of information there to be had. Go fishing!
For starters, congratulations on your first LD! Many more ahead of you, I’m sure. I have two suggestions that have proven effective in keeping me from losing lucidity. (I still “wake up” but never lose lucidity.)
The first suggestion is to engage very purposefully with the dream environment. Be sure to rub your hands together and rub them over your forearms. This will force your mind to convincingly “build” your dream body and really draw you into the story. (It’s also cool how real this feels – still impresses me every time I try it.)
Examine objects and constantly remark to yourself on their realism, always with the awareness that they are a creation of your mind in the dream world.
The second suggestion is to constantly keep your lucidity as part of the dream narrative. This could mean constantly thinking to yourself, “I’m lucid. I’m going to fly toward that building and see what’s inside. I know that I’m dreaming.” Sort of a sense of changing the inner dialogue from “Here is what I will do next” into “Here is what I will do next in this lucid dream.”
All you have to do is keep reminding yourself within your head that you are dreaming, and you will remember.
Engage all sense with the dream environment while telling yourself that you dreaming. Explore your dream body too
I’ve gotten into the habit lately of rubbing my hands together and shouting “lucidity increase” as SOON as I realize I am lucid, just as a precautionary measure to get the most out of my lucidity. It’s actually helped me, so give it a shot next time you realize you’re lucid. Best of luck!
In my first LD right after I became lucid I felt like the air had turned into very thick syrup and I could hardly move. To fix this, I yelled out ‘clarity NOW!’ This same thing might help when you become lucid to extend the amount of time you are lucid for, but I have never tried yelling it for that purpose.