Your bonsi is sadly dead now. Don’t give up. Find an other tree and try to collecting every information regards of the species before you buy it. For this one, it was too late to put outside, but with the next one you can have a good start. I think now you know that most of the tree species you need to keep outside, if you don’t want to spend your pants for a special system who can imitate the outdoor conditions with light, humidity and air movement. Read up about watering also, cause you cannot do it in schedule. Hope we can see your next tree thriving and sorry for your loss.