Hi @Allan Zalla ,
According to your description, you could try to use flow with approvals. Then you could create an approval process so that every time an employee adds a request to a SharePoint list, somebody receives a request to eidt or approve it. You could use "Grant access to an item or a folder" action to "automatically gains access to item". So this step "This group/user automatically gains access to the same item and can now fill in the second part of the formulary" also is possible.
For Example:
1.Add a trigger.

2.Add a profile action. Select the fields from your profile that you want to include in your flow.

3.Add an approval action. Configure the Start and wait for an approval card to suit your needs.

4.You could add condition you want.
5.And you could add email actions for approvals
6.You could add "Grant access to an item or a folder"

This article is an overview about using flows with approvals: Get started with approvals. You could get more details about flows with approvals such as single approvals, arpprovals with attachment and so on.
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