Germany's population grew 2 million, despite negative birth rate

How is this possible? German news media explains:

Despite a death rate higher than its birth rate, Germany managed to grow by two million people in two years due to high levels of immigration, statistics released on Tuesday showed. 

Immigration outstripped emigration by 1.15 million in 2015, slowing slightly to 500,000 in 2016. That accounted for a rise in the total population by around 2 million inhabitants in a three-year period.

What groups are the largest immigrants?

Romanians made up the biggest group of immigrants into Germany in the year 2016, the last year for which there are definitive numbers. In that year 222,300 Romanians moved to the Bundesrepublik. 

Syrians (179,000) and Poles (161,000) also migrated to Germany in large numbers in 2016. 

Interestingly, Germans migrated to Deutschland in the fourth largest numbers - a figure destatis explains through the fact that some 146,000 Germans either move back after periods abroad or were ethnic Germans who grew up elsewhere.

It's odd that there are no figures for Turks, Arabs, Somalis, Afghans, etc.