If you use 'do' before a verb, you emphasize, that you do that. For example, if someone asks you: 'Hey, do you listen?', you would answer 'Yes, I do listen!' to emphasize that you listen. You can also use this phrase to clarify a contrast. 'I don't like vegetables, but I do like sweets.' In case of a negative form, for example 'I don't listen', you would use 'I do not listen' to emphasize, that you don't listen. ;)

"I do listen" and "I do play" are stronger, more insistent forms of the simply informative "I listen" and "I play." Let's say your mom has complained that you never listen to what she says. You might counter with, "But I do listen!"

The "do" is understood, only added for emphasis, or to contradict an accusation. Such as "You don't listen to me." "But I DO listen to you!" Hope this helps.

Question: "I thought you don't play soccer" Answer: "I DO play soccer" If someone ask you a question (do/ don't) you respond back as it is.

The verb forms ('listen' and 'play') already imply an action is taking place in the present i.e. that you're doing something now so it's not necessary to include 'do'. However in the negative you would say I 'don't' listen. Example: I play football / I don't play football.