"vaali" kya hai?

Main ek doodh vaali chai lena pasand karunga, dhanyavaad. (In this sentence, does Vaali mean cup?)

No it means tea whit milk. So the question would be, what kind of tee do you prefer, plane or whit milk. and the sentens you provided is the answer.

Vaala/vaali is a useful word to know. It gives doodh the quality of an adjective. Doodhvaali chai = milky tea (tea with milk). Vaala is used a lot in Hindi conversation. Chaiwala is a seller of tea. Dhobiwala is a washerman. Delhiwala is a person from Delhi. So if you asked someone if they would like a cup of tea and they replied yes and added chiniwali it would mean tea with sugar or sugared tea. The ending will either be e, a or e depending on gender and plurality. I'm sure someone could write a whole book on its use! "Doodhwala" also means a milkman or one who sells milk! If the milkman happened to be a woman it would be Doodhwali.

vaali means about asking about getting something

Namaste, -वाला(vaalaa),-वाली(vaalee),- वाले(vaale) - suffix. Go with noun, adverb and verb. You don’t find suffix by itself. The 3 examples below are from the lessions. 1. हमारे पास यहवाली अभाग्यवश सिर्फ़ छत्तीस माप में है । Humare paas yehvaali abhagyavach sirf chattis maap mein hai. Unfortunately, we only have this one left, in size 36. यहवाली yehvaali = this one. 2. मैं एक दूधवाली चाय लेना पसंद करूँगा , धन्यवाद । Main ek doodhvaali chai lena pasand karunga, dhanyavaad. I’d like a cup of tea with milk, thanks. दूधवाली - doodhvaali - milky – also could mean a milkwoman. 3. वे लम्बे बालोंवली मेरी चाचीजी है । Weh lambe baalonvaali meri chachiji hai. The long-haired woman is my aunt. Weh lambe baalonvaali- The long-haired one. Here is another example of vaale: सब कुछ ऊपरवाले के हाथ में है। Sab kuch uuparvaale ke hath me hai. Everything is in God’s hand(s). Uuparvaale meaning ‘ the one up there’=God. घर ghar house + suffix vaalaa or vaali घरवाला – gharvaalaa - master or owner of a house. घरवाली – gharvaali(ee)- wife. Good luck in your learning Hindi! Namaste.