Blue card isn't citizenship. After getting the BC, one has to apply for citizenship. However that needs a few things one of those is being able to speak German.
The BC is just the first step. The real test is when you're offered to chose between the BP and the RP. Choosing the BP will fast track your application and you'll get your citizenship in 6yrs provided you don't leave the country for more than 6mo. You also have to blend in the German society and try and keep your head down. Take the BP. Trust me you can't handle the red pill
Germany doesn't allow dual citizenship last time I checked. There are some exceptions like your country doesn't allow you to give up its citizenship. In general it takes 8 years to become citizen. You would need to pass exam in German language as well. If you studied in Germany or show that you integrated well, the time can be reduced to 6 years. If you are in IT, then you are eligible for a blue card and after about 2 years you can become a permanent resident. This allows to avoid visa extensions. But if you leave the country for 6 months, you lose your permanent residensthip and have to start from scratch.
Thanks
This is slightly inaccurate because you can get a Blue Card on day 1. You don't need a Blue Card, you could also get a regular residence/work permit; it's just that the Blue Card comes with a few additional privileges, like bringing your spouse or long-term partner over without them having to prove they speak German at least at the A1 level, and getting an actual plastic card for your residence permit instead of just a sticker on your passport (the card still doesn't formally count as "official government ID" for the purposes of police/banking identity checks, but it's more convenient than having to use your passport for more things). A Blue Card does have to be renewed, but unlike a regular residence permit for work, a Blue Card allows you to apply for a settlement permit much faster, after 21 months of legal residence and tax/pension contributions if you can prove German B1 knowledge or 33 months for A1. A settlement permit is a residence permit that is not permanent (you lose it if you spend 6 months outside Germany or take up regular residence elsewhere), but it does not have to be renewed periodically anymore (so kiiinda permanent). Without a Blue Card, you can only apply for a settlement permit after 5 years of legal residence and tax/pension contributions. In any case, qualifying for a Blue Card only requires an authorized employment contract with a sufficient duration and salary for a priority occupation (e.g. software development) and a relevant recognized university degree. Also, it only takes 7 years of legal reaidence and tax/pension contributions to apply for naturalization if you do an integration course and prove you speak German B1. And in a few states, there are schemes where you can prove you have "exceptional integration" to German society (e.g. in some regions by creating a company that employs at least 5 people and is registered in certain industry associations), and then you can apply for naturalization after only 6 years of legal residence and tax/pension contributions.