Where you live, it should be outdoors for life, maybe protected from strong wind in winter, but that's about it. You have been watering too often and too much, and half that problem is the crummy soil it probably came in - peaty potting soil that holds water forever rather than letting it run straight through, and you fix that by potting in a lot of grit (small aquarium gravel is good) and some perlite and bark mulch. The one thing you shouldn't be doing is bringing it in and out arbitrarily (or at all) as it's confusing it more than anything. However if it's browning and the foliage is hard and stiff, it's gone, unless that's only one branch or something. I really suggest you start reading up on growing bonsai (www.bonsai4me.com is a good place) before you spend any more money - they're not house plants and need serious and specific care.