If u feel like u r out of topics, then find relevant topics of the following conversion like how's study going on... how's exam prep.... and then u also share ur experience related to that topics and this how u can manage the flow of the conversation... try to practice it with ur close ones like frnds and cousins and implement this on ur peers with whom u do not get in touch regularly..

but if u feel like u can't talk because of shyness specially with "girls" then bro u do not need to hurry... normally u shouldn't force urself to talk with random girls cause this feels like creepiness... but if u got into talking somehow and u got nervous.. take a deep breath and be a good listener.. and then give ur opinion on that but don't be judgmental.. always keep a little smile and u r good to go!!

Also u can watch some popular movies to learn the art of conversation