more tasks in the same row

Can I put more than one task in the same row?

Nope. If you need to have such kind of view - check timeline mode of dhtmlxScheduler … lines.html

Is it possible to have a day view or month view like a gantt chart with scheduler instead of a timeline ?
I like the possibility to see tasks per person.

You can configure timeline to show any amount of time ( day, week, month )
Also there is an unit view, which is like day view for multiple users