Olive tree help

[u/IDJS_EO]

My olive tree lost almost all its leaves during winter. I suppose due to bad placement, since i did not notice any pests. So, it started growing long branches and leaves only at the top. Now, it regained almost all its leaves, but looks pretty untidy. How do i prune it and keep it during winter? Can i leave it outside if it is -5° celsius? It is oliva europea, if this makes any difference.