Hi Maravilla,
Welcome to the forum
Everything about your schedule depends on your son's mood. To keep my son interested in the lessons when we first started I used to talk happily about them while we were doing fun stuff like playing on the playground. You can try showing the lessons while he is snacking or after an activity that has taken some of his energy. The is to always follow his mood and if he does not want to watch try again the next day. I have noticed if a coupe days or more goes by without the lessons my son is more attentive when they are resumed.
In the beginning I was showing my son Little Math, LR English and Chinese session 1 in the morning and session 2 in the evening.
By the time LMs was released he was reading in English so we stopped those lessons gradually.
Since then we have added French, Spanish files and Encyclopedia Knowledge files. So each session of BrillKids takes us about half an hour. Sometimes I split one session into two and try to catch up over the weekend.
Yes you can definitely teach all languages simultaneously. I usually try to plan our extra lessons so that he is learning the same words in all the languages.
Looking forward to hearing more about your early learning journey