then noticed that no one touched it and I will then add my opinion.
First, unless your wallpapering the walls I do not know why you would want to have smooth walls. Texturing does add a finished look to all wallls and smooth walls just look unfinished.
Anyway, you can skim coat the existing walls to achive the smoothness you are seeking. It may take two or three coats to get there. I would do this first, prime the walls with a latex primer. Let dry then begin your skimming. dilute the joint compound down pretty thin and apply the compound with a 3/4 knap roller cover then when on the walls skim it out or float it out. Allow to dry for a day then apply another coat. after dry then lightly sand to smooth out any imperfections. if satisfied, then prime it again and then add your finish coat.
Do not do this if the weather is damp humid, ad this will take the drying process much longer. Might use a 45 minute compound, when adding water it will lengthen the drying process, but still.