How to make out whether the German for table is Tabelle or Tisch?
Without context, it could be either. Note that a Tabelle is a table in the sense of information presented in rows and columns, while a Tisch is a piece of furniture with a flat top surface.
I wrote 'Dieser Tisch ist grosser' (I did not not umlaut the o) and Duo accepted it.
Was Duo too lenient on me?
Me too. It gave the umlaut as an alternative answer, but it is wrong to leave it out isn't it?
the word 'grosser' does not exist, it has to be größer
Per revereo.net großer (or grosser) does exist, while größer is preferred. Perhaps a native speaker can enlighten us as to the difference.
Yes Duo was too lenient because it does not mark you wrong for missing an accent (but it should) and it accepted "ss" for ß in case you couldn't type ß, but it should have been größer
What is the difference in usage between großer and größer