I have the latest version of KDENLIVE
I Have the latest version of Kubunu

Size source Gopro (PAL-1920*1080 119.88FPS) are 145,8 Mio
Size out are 2,4 Gio (without song) -

I used H.264 (libx264+acc) to do this

I think there are a problem because size must be under the init size, isnt'it (that was with the old version of Kdenlive)
Wath's wrong ?

PS : Sorry for my English

Check h.264 quality render settings:

Lower number = higher quality = bigger file
Example: quality 22 gives 99 MB file, quality 15 gives 270 MB file

Or post your complete render settings here. Filesize must not decrease when rendering - it depends on the bitrate. If render bitrate is higher than the original, filesize will grow.

Thank you
I juste want the same quality than the source
Source are Gorpo (Héro Black 4) ; 1080 120fps
I want to cut it to 1080 50fps (PAL), that the reson i hope to have the same qualty but under the source size because i cut it and i change the fps.
I do tha isn't it
properties=lossless/H.264 g=50 but it dont work....

Lossless rendering is done with very very high bitrates - around 120 MBit or even more. That results in 15 MByte per second rendered. So, if you use lossless rendering profiles your filesize will always be veeeeery big.

You can check the bitrate of your GoPro camera running the command ffprobe <yourgoprofile>
The output will show the bitrate of the clip someway at the end of the output.

Knowing the bitrate, check the MP4 section for a profile with h.264/high profile in kdenlive. There you can set the quality (slider or in the details of the render profile) and find a compromise between filesize and quality loss. You may want to create a custom render profile with the results of your experiments. BTW: Rendering always gives a loss, but usually it will not be visible for your audience.

If you want to have roughly the same bitrate as the GoPro, render a short piece of your project and check the result with ffprobe until you have a setting matching your needs.