Hi Armin

Both the Helpdesk and CRM modules in Odoo can be useful for your business but they serve different purposes and cater to different aspects of customer interaction it seems you are looking for customer service more than a sales  If most of your emails are related to customer inquiries about problems with products, service issues, or requests for assistance, then the Helpdesk module is more appropriate. and also you can achieve most of the functionality of  CRM in Helpdesk as well with minimal customization.
if you have further question's please don't hesitate to contact me

Regards...

Hi Armin,

Here I have provided a basic overview of the Helpdesk and CRM modules.

 =>Odoo Helpdesk is a ticketing-based customer support application.It allows you to manage tickets according to phases such as New, In Progress, and Closed.You can prioritize tickets to address customer issues quickly and efficiently.
    The Helpdesk module is ideal for projects involving:
    =>Remotely assisting clients with technological issues.
    =>Answering client queries, issues, and complaints.

 =>CRM  is a customer service and support module that helps you manage customer inquiries and issues.It helps you organize your sales activities: track leads, close opportunities and get accurate forecasts. Keep opportunities organized with the pipeline and manage your day-to-day activities with meetings and next activities.

As per my point of you If most of your emails involve customer inquiries about your products and services, the Helpdesk module is ideal. It includes CRM functionality with minimal customization and at a low cost.

Thanks.