next time please use google translate to convey your ideas correctly, because I can barely understand what you're asking:
https://translate.google.com/?sl=auto&tl=en&op=translate
But if I'm understanding you correctly, the reason your manager tells you to buy a domain and set up a blog is because....
1) having your own domain instead of posting your company on 3rd party sites (yelp, tumblr, etc... although these have their purpose too) will make you look professional.
I am sure you agree that a website like
nike.com looks better than
nike.yelp.com
2) if you want to rank in google you will need to churn out a lot of content (because google loves content, and tends to send traffic to sites that have better, more, and more frequently updated content), and for this purpose blogs are great.
3) if you have your own domain you can do whatever you want with it, and a company that has no website in the age of the internet is almost as if that company doesn't exist.
But anyway - as I was saying - having your own domain grants you 100% control over your online business, whereas if your site was on tumblr.com (just an example, I might as well have said medium.com, or LinkedIn.com, etc) you would be at the mercy of those 3rd party sites, which would suck as a business because... well, because of many reasons that I'm sure you can see, I don't have to explain them
It's one thing to post whatever you want on your site instead of having 3rd party sites like Tumblr, Reddit, Medium, etc police your activity and tell you "no, we don't like that, you shouldn't be posting that" and then deleting your money-making content just because it's against their TOS...
because of what I said earlier: google LOVES content, and - when they find fresh, quality content - they will want to index it so that their users can benefit from it. And blogs are great at showcasing tons of quality content, which is why they are "best of the best". At least in this regard, in others they are not best of the best