Hi Nico,
Looking at your business case, it looks like post qualification of lead you are creating only opportunity, and post winning the opportunity you want to create contact first and then create the account by converting contact to an account.
As the lead qualification is part of your business case, we would like to suggest the following:
There already exists an OOB lead qualification process where there is the automatic generation of Opportunity, Contact, and Account records after clicking on the qualify button on the lead record.
When the lead is qualified (when clicked on the qualifying button), the following entered values on the Lead record play role in the outcome of the OOB lead qualification process:
- Name (First Name and Last Name):If this value is entered, it becomes the full name of the new contact record.
NOTE: Last name being a mandatory field is entered always by the user hence contact record will be created always in lead qualification along with opportunity.
- Company:If this value is entered, it becomes the name of the new account record.
NOTE: “Company’ being a business recommended field is not entered always by the user hence account record may or may not be created in lead qualification along with opportunity.
You can find the below screenshot where the Contact and Account records were created/converted through the OOB lead qualification process:

Also optionally, you can control the above OOB lead qualification process from App Setting as below:
Under Sales hub app > Change the area > select App Settings
Under General settings --> “Lead + Opportunity Management” -->Go to Lead Qualification” by default this setting is Yes means qualifying the lead Account, Contact, and Opportunity created as explained above.

But if this setting is set to ‘No’ then while qualifying lead record you can choose only those records which you want to create.
When you try to qualify a lead, you will see the below page where you have the flexibility to create or skip record creation amongst Opportunity, Contact, and Account records.

If you find this useful then mark it as verified or let us know if we can help you further.
Hope this helps.
Thanks!