One is to get some T posts and with a manual pile driver, drive them along side the Outside of the wall to keep it from topling over. You can also use line posts or king posts used on chain link fences to do this also. T posts are cheaper but not as strong.
Its very hard with what you have to make it stand up again straight, but all you can do is to keep it from further falling down.
Consider diging a trench perpendicular to the wall and lay a tie in the trench and fasten it to the wall with 12 inch pole barn nails and then bury that post in the ground. Drive some barn nails in the opposite end of that tie to keep it in position.
Good luck. try to find old ties that are not leaching creosote so badly. This is bad on hands, carpet and adjacent grass.