textbox to first empty column in activecell's row

Hello,
I am trying to create a database / userform with excel. In the databse every row is a different person with different variables (columns). A certain variable can get more then one value (i.e. column1 : var1; column2 : var 2). The number of columns deponds on the person. What I want to achieve is that whenever this var is introduced in my userform it shall be put in the last empty column of that row.

I have tried something with myrange and selecting the row (column a is the column with the user-id)

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And now I am drawing blanks and getting a lot of errors. What am I supposed to do?