slow performance with cursor

I am using postgresql 12 and using cursors in a stored procedure, executing procedure which has cursor is slowing down the call. However if I do not use the cursor and just execute the queries using JDBC (Java client) it's fast.

Is there any setting which needs to be modified to improve the performance of cursors. Also facing slow response with reading blobs (images) from db. Not an ideal way for storing images in db but this is a legacy application and wanted to check if there a quick tweak which can improve the performance while reading blob data from db.

--Ayub