Oui il suffit de réinstaller Android avec flashtool, télécharger votre Android pour votre appareil ,puis aller dans Android et changer le fichier gpt par un gpt modifier et flasher normalement, il vous resteras a peu près 25 go de libre. Voila
I guess you no longer need the information, but I leave this link in case it serves other users. I did this process in my Hi10 Plus.
Watch this thread: https://techtablets.com/forum/topic/resize-android-partition-the-easy-way-for-x98-serie/
You have to adapt it to your tablet with the correct rom and use the .bin file closest to your internal storage, in this case it has to be gpt_20g_org.bin Since your tablet is 32GB.
Remember to replace this file before flashing the Rom and rename it to gpt.bin