A tip I use when translating from English to Spanish, the '-ing' form in English is often translated into the infinitive form in Spanish. The only time the '-ing' form and the -ando/-iendo form directly correlate is when it is phrases likes "I am running" "Estoy corriendo" "I am swimming" "Estoy nadando". If it is a phrase like, "I like swimming" or "Running is good for your health" translate the phrase by using the infinitive in Spanish e.g. "Me gusta nadar" "Correr es bueno para la salud." It is all about understanding the role of the '-ing' word in the sentence in order to anticipate whether or not you use the '-ando/-iendo' form in Spanish.

I would rather say "Quiero practicar la conversación", if you say so native speakers will understand you.

Actually, I think we have no an easy translation for that. Maybe the most suitable is "Quiero practicar el habla".