What language do they speak in belgium

There are actually three official languages spoken in Belgium, in addition to many more spoken by immigrant populations. The two most prominent languages are French, spoken in the south of the country (a region called Wallonia) as well as in Brussels, the country's capital, and Flemish, a version of Dutch that is spoken in the north of the country. There's actually significant tension between these two language groups, who for years have argued about splitting into two countries.

German is also an official language in the country, though it's spoken natively by only a very tiny portion of the population near the German border. 

There are also a ton of funky little dialects of all three of these languages, like Limburgish, Walloon, Picard, and Champenois, but none of these dialects is an official language in Belgium.