Yes/no questions: да ли and ли
Ten minutes of the grammar lesson's own rule: a yes/no question either opens with да ли and keeps the statement's word order unchanged, or moves the verb to the front and attaches ли right after it, second position, exactly like any other enclitic. Build three questions choosing the opener a plain yes/no question actually needs, then hear a да ли question said aloud.
The part of the grammar page this lesson drills — read it here, then use it.
Yes/No questions: да ли and ли-inversion
Да ли is the safest way to ask a yes/no question: place it first, then keep the statement's normal word order unchanged. Да ли говориш српски? (Do you speak Serbian?) is literally Да ли + Говориш српски.
The alternative is ли-inversion: move the verb to the front and attach ли directly after it, in second position, like any other enclitic. Говориш ли српски? asks the same thing. With бити, the long form combines with ли: Јеси ли уморан? (Are you tired?) - see the lesson on the verb бити.
In a yes/no question, ли can never stand at the very start of a sentence, and can never attach to a noun or pronoun directly - it leans on the conjugated verb leading the clause.