Riemann's collected works (much shorter than most great mathematicians, because of his early death) are published in German https://www.cambridge.org/core/books/bernard-riemanns-gesammelte-mathematische-werke-und-wissenschaftlicher-nachlass/EAB8B46090AFADB656CE9E5969F0A03B.

Here are the original papers in German: https://www.emis.de/classics/Riemann/index.html

There is famous translation of one paper in Spivak's Comprehensive Introduction to Differential Geometry.

Here is Riemann's famous Ueber die Anzahl der Primzahlen unter einer gegebenen Grösse, a paper on prime numbers: https://www.claymath.org/publications/riemanns-1859-manuscript, with an English translation.