Foreign Data Wrapper - mapping nvarchar datatype

Question

I have linked a SQL Server database with a PostgreSQL database via tds_fdw extension .

I mapped SQL Server tables into PostgreSQL foreign tables. Connection successfully.

I have got problem on mapping nvarchar datatype to Postgres. I mapped nvarchar as varchar, because SQL Server varchar and nvarchar is the same for PostgreSQL. But nvarchar columns didn't mapped correctly (stored as ? for some symbols).

How can I correctly map nvarchar from SQL Server to an equivalent datatype in Postgresql ?

I created Postgresql database with an UTF8 encoding