I'm no expert, but I'm thinking your bonsai might be a privet. Maybe someone else can check me on that. Why are you thinking it might die? It looks healthy.
If I am right, privet is a tree that does pretty well indoors for the winter. It needs good general bonsai care: water only when it needs it, not on a schedule; bright indirect light. Check out the bonsai care articles here: https://www.helpfulgardener.com/bonsai/
and here: https://www.helpfulgardener.com/forum/vi ... =36&t=1479
It doesn't look like it is in good bonsai soil, which is more mineral and free draining. In the spring, before you take it outdoors for the warm season, re-pot in to real bonsai soil.