Learn French: Ce geste est très impoli ici. - This gesture is very impolite here.

In French, not all words ending in "e" are feminine! Geste is actually a masculine word. Because it is masculine and starts with a consonant, we use the masculine word for "this": ce. If it were a feminine word, you would use cette.

How would impoli change if we were talking about a feminine word instead of geste?

You would need to add a silent "e" to the end to make it agree with a feminine subject. For example, if you said "this action" (cette action), it would be Cette action est très impolie. Here, it stays impoli because geste is masculine.

Is there a liaison (linked sound) between très and impoli?

Yes! Because très ends in a consonant (s) and impoli starts with a vowel (i), you usually link them together when speaking. You will hear a "z" sound connecting the two words, sounding like "trè-zimpoli".

Since this lesson is about giving advice, how could I follow up this sentence with "You shouldn't do that" using devoir?

To give that advice, you would use the conditional form of devoir in the negative. You could say Tu ne devrais pas faire ça (informal "you") or Vous ne devriez pas faire ça (formal or plural "you").