I started backlink building of my site 5 days ago and today my site is on rank 65 on google search results for the two keywords that I do optimization. It is a highly targeted niche. When google can penalize my site? When I start to build too many backlinks or when I start to build them to fast? Do I need to stop for some days and after that to start building again? And is it worth to put backlinks on sites that is not relevant to mine ?