Learn Hardcore Spanish (Spain): Habla con su muñeco como si entendiera todo lo que dice. - She talks to her doll as if it understood everything she says.

Breakdown of Habla con su muñeco como si entendiera todo lo que dice.

Why is there no subject pronoun before habla?

Spanish often drops subject pronouns when they are not needed, because the verb ending already gives information.

habla can mean he/she/it speaks or you speak (formal singular, usted)
In a full sentence, context usually tells you who the subject is

So Habla con su muñeco... is perfectly natural without él/ella/usted.

What does su mean here, and whose doll is it?

Su means his, her, your (formal), or their, depending on context.

So su muñeco could mean:

Spanish su is more ambiguous than English his/her/their, so you often need context to know exactly whose doll it is.

Why is it muñeco and not muñeca?

Muñeco is the masculine form and muñeca is the feminine form.

So this sentence specifically says muñeco, not muñeca. It could also refer more generally to a toy figure, depending on context.