Hello Celine Obringer!
Your English is very good 
I think there are some different ways you could accomplish this.
The first that comes to mind is to do a Query List on the user ID, in Descending by Created date, and capture that one item (probably the item URL or ID) in a variable.
However...
I am a bit confused by: "Two weeks later Andrea wants to complete her request, she needs an access to another Sharepoint Site and wants to edit her previous request in order to complete her previous request."
Do you mean, she wants to create a new request based on the same information from her previous one? So she does not need to copy all of that previous data?
Am I on the right path..?
Cheers,
Rhia
Hello Rhia Wieclawek
Thank you for your answer
I was busy these last days and couldn't answer sooner, sorry.
You're on the right path 
I tried to do a Query List bue no success 
What I want is un button My Profil (Mon Profile) which would redirect the user to his( her) original form. (First Picture)
One user would only have one item in the list and complete this item each time he (she) have a new request. (Second Picture)
But I'm in trouble with the item ID
mysite/fr/mysite/mysite/Lists/Request/EditForm.aspx?ID=41&Source=https****
I want this ID, in this case 41, to be linked to the CurrentUser who's logged to the website, so when the user push My Profil (Mon Profile) his (her) personnel Item.
I thought about something like that mysite/fr/mysite/mysite/Lists/Request/EditForm.aspx?ID={CurrentUser:ID_User}&Source=https**** because each user has a personnal ID in this request form, but I really don't know how to perfom something like that.
Kind Regards
Merci pour les details!
From what you've said here, I understand that the user has ONE other form, or a previous form, that will hold the information you want to pull into this NEW form.
Is that correct?
For example...
I come in, and fill out a form. I am Rhia. That form's ID is 41. I submit it.
2 months later, I come in, and fill out a form. I am rhia. THIS form's ID is 82, but, I want to push a button that will A) find the previous form that I entered (41), and 
pull in the data from that form for fields X, Y, and Z.
Is that accurate?
Hello Rhia,
Thank you for your answer, that's really nice.
The user only have one form.
The scenario is :
I come in, and fill out a form. I am Rhia. That form's ID is 41. I submit it.
2 months later, I come in, and (fill out a form. I am rhia. THIS form's ID is 82, but)*, I want to push a button that will A) find the previous form that I entered (41), and pull in the data from that form for fields X, Y, and Z.
* I want to bypass this step et I only want this part :
I come in, and fill out a form. I am Rhia. That form's ID is 41. I submit it.
2 months later, I come in, and I want to push a button that will A) find the previous form that I entered (41), and pull in the data from that form for fields X, Y, and Z.
The button would start an action which would recognize the user because he (she) is connected with his (her) AD account but I don't know if it's possible to start a Workflow without creating or modifying an item.
Kind Regards
Okay, so I did some thinking around this, and here are some options for you ...
You can start a workflow from a button -- take a look at these posts:
https://community.nintex.com/thread/2712
Just letting you know that's possible.
What you could do, though, is do a look-up in the form itself -- "look for this user, in this list. if you don't find it, don't worry. but if you do find it, then fields X, Y, and Z, should be filled with data."
So I think that would become a look-up rule of some sort.
I would need to test this out ... I might just... !
Just wanted to let you know I'm still thinking about it
Hello Rhia,
Thank you for your answer, I really appreciate your help
I will take a look a the post you mentionned and do some tests as soon as I can and tell if it works !
Kind Regards
We will test together 
I still have your issue in mind - but I have been at InspireX all week! Hopefully I can look soon.
