Adobe Signature lock on send

Hi!

I am almost finishing my pdf contract but i have a question.

I have multiple text fields which i dont want the customer to edit, but i still want to be able to edit them myself because there are things that need to be changed depending on the prices etc. 

Example i have "personal information" for the customer, i want him to fill this out himself but lock every other text field i have already filled out. Also i would need him to Sign in the sign fields. 

I have tried making a signature field with certificate for myself to lock every text field except those i need the customer to fill out. But this locks the whole contract so i cant send it to the customer for signing. 

"Be om signaturer" = (Ask for signature) is not able to click on (Including a picture) This is after i signed it myself via the Certificate.