Please do not judge my choice of equipment, that is what I got, and I have to work with it.
That's going to make it tricky.... 😉
I always get background noise
I'm not sure what you mean by this. A sensitive mic will always capture any quiet sounds around, particularly if there isn't any loud "foreground" sound to drown it out. If you're recording nature ambience in the forest, then "background" sounds is exactly what you want.
If there's a road nearby, with cars passing, then there's no way to separate that from the general sound of wind in the trees, etc., except to move away from the road. This can be hard -- when recording forest ambience at dawn, I have found that a busy road 1 mile away is clearly audible. The shape of the landscape will help, if there's a hill between you and the road, for example.
If there are planes going overhead, and ruining your recording -- well, all I can do is tell you that field recordists the world over feel that pain.
On the other hand, if there's some specific foreground sound that you want to capture, then get the mic as close to it as you can. Sound falls off with the square of the distance -- get 3 times farther away, and it's 9 times quieter -- so use distance to select the sounds you want. When recording a babbling stream, for example, my usual terchnique is to find a specific spot in the stream that makes a nice sound, then put the mic within 30cm of it.
The point p4pictures made about using manual levels is important too.
and with even slightest wind "DeadCat" does not seems to be working.
Make sure that your camera is set to use the external mic, not the built-in mic. This can be surprisingly tricky with modern cameras. I always put headphones on, then scratch the various mics with my fingernail to make sure which one I'm actually hearing.
The Rode DeadCat is a good choice for your mic. I would expect it to help in a slight breeze; but bear in mind that there is no wind protection that can work in a strong breeze. Even the best blimp windshield will be overpowered eventually.
For what you're doing, you may find it helps to record the sound separately from the video, unless you specifically need them to be synchronised. I don't just mean into a separate recorder, I mean at completely different times. That way you can concentrate on placing the mic to get the best sound, without worrying about it being in shot, and edit out cars and planes, for example. In other words shoot your video, then become a field recordist to capture the sound to go with it.
What you're attempting here is really cool, and I really hope you can get some success with it. Just be aware that recording good quality nature ambiences is surprisingly tricky; people make careers out of this. I made a series of videos on field recording, which might be of help if you're interested: https://moonblink.info/FieldRecording
All the best.
