Best thing would be to call in a suitably qualified and experienced locksmith. If you were to reassemble that incorrectly the door might jam causing what we call a “lock out”. You don’t show an image of the key, if you have one. Perhaps that is for security reasons, I can imagine you not wanting to release an image of the key over the internet. The point is that a really good locksmith, specialising in this type of work, might be able to produce a functioning key for the lock at the same time.
If you could remove the door, you could take that to the locksmith and thereby save yourself his call out charge- but do that only if you are confident that you can reinstall the door correctly- otherwise you will have simply exchanged one problem for another.
