Hello Greetings!! I found that you want to integrate the payment gateway on your accounting system (Sevdesk).
We have applied a different kinds of payment gateways in many websites and are expert in it so we can handle your project easily.
I have vast experience with payment gateway integration (PayPal, strip) and this because of professional experience of 7 years in MEAN/MERN and mobile development and designing.
Moreover, It would be great, If you open a chat box for further discussion, So we can discuss the project in detail and accordingly provide you proposed solution.
Warm regards,
Jatin
Price mentioned is just a placeholder