The photo shows a wall with graffiti written in Turkish. It says "Yıkılmadım ama ayakta değilim". The joke is a play on words using the word "ayakta" (standing) which can also mean "on foot." The person who wrote this is implying that they are not standing on their feet, because they are so tired they can't even stand. The humor comes from the unexpected twist in the phrase, which is common in Turkish humor.