When our scooters are being assembled all the bolts have a thread locking fluid applied to them to ensure that there is minimal loosening and movement of the parts. This can however cause problems when trying to undo the bolts.
If you are finding any bolts too tough to move a short, sharp tap with a hammer can be enough to break the seal of the locking fluid and make it a bit easier to handle.
You may find you need a little extra force to tighten or undo the bolts, even without locking fluid causing the problem. If you place a short length of pipe or something similar over the handle of the Allen key this should give you the added leverage you need to undo or tighten up any bolt.