Hi Romansv,
Sorry for the delay in response.
As you need to fill and sign the document after the other signer complete the form, you need to add your email address as a second recipient.

Then make sure that you check the box for "Preview and Add Signature Fields" at the bottom of the page before clicking the Send Tab.

Then you need to assign the form fields for the signer and that needs to be filled by you.
Take help of the steps mentioned here Assign form fields to recipients.
Then you will be able to fill and add the signature to the document after the client completes the form.
Hope the information helps.
Let us know if you experience any issue.
Regards,
Meenakshi