You have to put the auxiliary before the verb it can be « sommes montés » or « avons montés », it depends of the context.
Well, this is not an easy question, as it's hard to say what " practically noone" means.
In Cote D'Ivore, most people are either Muslim or Christian, so it's definitely true that most people are not practicing traditional religions.
However, an estimated 3-10 percent of the population still practices traditional religions and some fuse elements of traditional religions with Christianity or Islam.
So I would judge the statement as "false" that "practically noone" - since some people do!
Answer:
À mon avis, jouer à beaucoup de jeux peut être très dangereux pour la santé.
Translation to english:
In my opinion, playing a lot of games can be very dangerous for your health.
I think it means how many are you in your family.
Imparfait would be the description of a situation for example :weather, landscape, person in the past whilst passé composé are actions that suddenly happened for example, interrupting another action. Passé composé you would also use an auxiliary like either avoir or être then you would add the verb
