Full credit to alecxs for this answer. Posting incase anybody else has the same problem in the future.
Download stock image(Mine was oneplus.com/uk/support/softwareupgrade/details?code=9)
Use extract_android_ota_payload-master to split the payload.bin inside the zip
(Method for step 2 https://pastebin.com/RfEHuvu7 , I did this on linux because my linux ...
If you have the habit of removing apps on a regular basis, then you can clear it regularly. Once a year or once every 6 months should be fine. If you have root, then you can use Titanium backup as stated on this answer to remove dex files not link to apps.
I have found a workaround to enter in recovery.
a)Turn off device
c)We enter in bootloader mode, with volumeup key we select the "recovery" and press power
d)Device reboot to twrp
The basic process of installing TWRP on every phone is to boot into TWRP itself first so TWRP could overwite the recovery partition and replace the stock Android recovery with TWRP itself.
Boot into bootloader / fastboot mode
Make sure that your device's boot loader is unlocked. If not, please follow this tutorial on forum.xda-developers....
Thanks for that really detailled answer, dear alecxs.. At first it didnt work because i had the wrong ROM , than i take the correct one , followed the tutorial really exactly from 1-20 and what should i say , i reanimated this Tablet which stucked in a bootloop a long while. Workes well now .. I struggled a little bit with Google Play Services which i cant ...