It is pretty simple: if you want your juniper to live, it needs to be outside. if it has been inside, and only inside, and you have really cold temperatures like below freezing, it might be a good idea to find someplace unheated that stays above freezing but gets a lot of light. when I was young, I had three junipers like yours, and insisted on keeping them inside... not one of them lasted longer than a month. Junipers, as has often been said here on the forum, when kept outside can endure up to -10 or lower.
the tips browing is not a good sign.. needles on the inside browing and falling of is normal, that's how the tree grows. It looks like you have some fresh growth, which is a good sign, but also a bad sign, junipers as with most trees go dormant in the winter.
try and see if you can take the rocks off the soil, if you can and you see normal potting soil. they probably will interfere with watering.
www.bonsaiempire.com/tree-species/juniper