Try renaming and pushing build2.prop.
That will tell you if there is a problem overwriting build.prop (in which case you could move it out of the way, or problem with writing to /system in general)
Also I assume you are doing the adb push in TWRP, not in android.
I think that the problem is:
Now i have root systemless
But I need to root system also...
How I can solve this problem and have a normal / full root (NOT Systemless!!!)
i found this guide: Some opinions????
Step 1: flash SuperSu 2.71 normally (this will patch boot.img)
Step 2: boot the device and full unroot in Supersu app (device should now
be unrooted, however because of step 1, the patched boot.img is still there)
Step 3: boot into twrp >go to the terminal > and type: "echo
SYSTEMLESS=false>>/data/.supersu" (force the new 2.71 to only install in
Step 4: now flash supersu 2.71 in twrp (if you read the logs, it should say
something like "installing in system mode")