That's a huge gate! You have a lot of considerations that perhaps you need some help with beyond what you can get here. Your foundation will be similar to a cantilever traffic signal foundation, typically a drilled pier foundation. Yes, you will have to accommodate overturning from wind. You will also have to consider a torsional moment in the event the gate gets slammed against its rotational terminous during a wind event. Further, this would be a dynamic event, not static like the other considerations you'll have to make.

I would suggest you get a local structural engineer and a local geotechnical engineer involved to assist with this. This is not a simple gate structure.

Bruno64:
You might be better off to redesign the gate as follows, it might simplify the gate and foundation designs, and also improve the operational mechanics.
1. Put wheels under the left and right bot. corners of the gate. These might be “V” grooved steel wheels made to run on an angle iron runner with its toes down, or just on an upstanding steel bar (1” x 2” high). Put small plow bars in front and back of each wheel, almost touching the upstanding stl. bar to clean it off with gate motion. Maybe a center wheel too, to reduce gate bending moment. The gate can now be about 13-14m long, (your “B” dim. +) since you don’t need the 5.3m (your “R”) backspan any longer.
2. The primary foundation then becomes a conc. grade beam, in line with the gate motion, to which the above upstanding stl. bar, runner, is fixed. Maybe with a horiz. bot. flange fixed to or into the grade beam. This runner bar and the grade beam would be about 25-26m long, (13-14m + 12m) for full motion of the gate.
3. You still need the left hand post, one post on the right in your sketch (not two posts), and maybe another at the full gate movement, or .75 gate movement, further to the right. These posts probably have to be set in drilled piers to take the lateral loads, wind and the like. At the right post (or posts) you need guide wheels running on the top and bot. gate rails (both sides) to guide the gate movement and take the lateral loads into the posts.
4. The top and bot. gate rails (your “1” & “2”) need to be fairly stiff in the horiz. direction to take the lateral load bending of the gate. But, you no longer need your bot. “slide profile”. There is some confusion about the numbering here (“6” or “8”)?

A quick evaluation yields the support forces as shown below. Note that only the weight of the gate was considered, with the gate was just moving away from the leftmost support. The results indicate the 50cm pad foundation is unrealistic, I think you will need a pier foundation, or pile foundation, to keep the rotation in check. You will also need to consider wind and earthquake load, if applicable. As suggested by Ron, you shall looking help from a structural engineer. Also, you will need to consult with a geotechnical engineer for the capacity of the soil, and for stability/settlement concerns. Good luck.

Maybe someone has already suggested it, that you can get away from the rotation by adding wheels to the left end of the gate. By carefully design, it would also help the stability in direction transverse to the gate.

On further inspection on your drawing, it seems there is a wheel on the left edge. If that is the case, please disregard my suggestion to use deep foundation, as the pad foundation should be fine. Is the wheel running on/in track? I suggest to have a pair of wheels, one on each side of the gate to help in stability.

Dear Ron, dhengr and r13,

many thanks for your feedback. Well, to be honest i did follow as per cantliver gate maker "ROB" for the calculation but not sure if for the concrete foundation they are taking into the account the wind load :
http://www.rob-systems.be/productbuilder/variazelf...

As suggested, i will follow yur recommandations and consult a geotechical engineer.

Best regards and happy new year

Bruno

Dear Bruno64 (Industrial),

I looked to the calculation report provided by the supplier.

Apparently they have calculated the wind but did not consider accidental force ( impact etc)..

The proposed ftg size = 5.8m L, 0.8m H , and 0.5 m W ..

The max . soil stress σs > 50kN/m2 .. which should be around 20 kN/m2 .. check the soil conditions ..

I will suggest to increase the width.. around 0.8 m. better change the width with depth if there is no geometric restriction for the erection of rails etc.