Hello @Yoan BITAR , apologies for the delay.
First of all I just wanted to confirm as per the documentation you can only import Functions based off HTTP trigger with Anonymous or Function authorization levels.
If above check is fine. As per this stackoverflow question, it looks like might be a browser issue and doing a hard refresh might help in resolving the issue. If this does not help you can try and change the browser and see aswell.
Additionally you can also try importing the Function app via VS Code as shown here
Please let me know if this helped in resolving the issue or not, I will be glad to continue with our discussion. Thank you!