Will my transplanted beard get thicker? I did my transplantation 7 days ago and they are very thin

You cannot tell how "thick" your beard may be until it grows out in 6 to 12 months.  You also should have been told how many grafts were transplanted so you can have a general idea of what to expect.

The transplanted hair usually falls off and it will start to grow in after a few months. It takes up to a year for all the hair to grow in. Initially the hair that is growing in is feathery and fuzzy but it thickens up in six to twelve months. 

Now that you did the beard transplant, you must wait out the results which usually starts growing some 4-6 months before enough hair has grown and then the results will magically appear at 8-10 months from the time you had the beard transplant

Zdravo! Any hair transplant patient must be willing to make a time
commitment before they can fulfill their dream of new hair growth. After a hair
transplant, the new growth will normally begin in 3 to 4 months, but you may have to wait a year or longer to see permanent hair growth in all
of the transplanted areas. Your doctor can give you more information.