There is an English translation of the collected papers of Riemann, in $2004$. It says "This is the first English translation of the collected papers of Bernhard Riemann (1826-1866), one of the greatest mathematicians of all time. Riemann surfaces, Riemannian geometry and the Riemann zeta function are fundamental concepts of modern mathematics." And so on.
So, here are a few directions you may wish to explore for formalizing natural language, which is a broad topic. From looking a bit, this question does not appear to be an exact duplicate of an earlier question, but there may be some other questions such as this one that will help.
One is formalized systems that resemble natural language.
This includes the Mizar system which is a piece of software that validates proofs written in a syntax that's like a cross between a programming language and mathematical prose. There is a Proof Assistants Stack Exchange with more information on Mizar and other proof assistants.
One direction might be studying metalogic.
Metalogic uses natural language to avoid circularity, but its use of language is different from natural language in other settings. In particular, metalogical if is the material conditional, usually.
One thing to check out might be the Open Logic Project which has a few free and open source textbooks on logic. Boxes and Diamonds, the book on modal logic, covers some approaches to formalizing the notions of possibility and necessity (and some other things like time and deontic status). It includes a lot of examples of explicit metalogical analysis using Kripke frames.
One direction might be cataloging the difficulties we would run into if we attempted to formalize natural language.
Aside from the difficulties with quantifiers mentioned in the comments, such as in the famous example someone loves everyone. The connectives themselves like and, or, not, and if are tough to formalize. A compelling account of all of their usages is elusive.
The Connectives by Lloyd Humberstone, has examples taken from natural language of different kinds of phenomena that defy a straightforward encoding in a logical system. This book is quite big and full of technical details about different logics, but the introductory sections on the chapters about specific connectives have good examples of natural language use.
Best Answer
Some possibilities of finding the translations which I am aware of.
Wikipedia. Surprisingly, quite often, when I look at an article at English Wikipedia, I find translation of the term by checking language mutations of the article. Of course, this works better only for Wikipedias that are large enough.
Wiktionary is a free online dictionary, which is built collaboratively. It seems that it contains some mathematical terminology, see e.g. Category:Mathematics or Category:Group theory.
There exists the following book: Dictionary of mathematics, English-German-French-Russian, Berlin, VEB Verlag Technik, 1982. (Günther Eisenreich; Ralf Sube). This dictionary is organized into two parts; one with words, each word having some code. E.g. C1623, complexity, Komplexität, complexité, сложность. The second volume is a register in which you have (for each language) alphabetically ordered words with the codes, so that you can easily find them in the first volume. In this way it is relatively easy to add new languages (you only need to add the part with pairs between terms in this language and the code used in the book). I don't know whether such additions were published in other languages, too, but I happen to have this dictionary where Slovak language is added: Matematika: anglicko-nemecko-francúzsko-rusko-slovenský slovník. Bratislava : Alfa ; Berlin : VEB Verlag Technik, 1982. When I find a mathematical term in this dictionary, I consider the Slovak translation from this dictionary as a standard. Here are examples what the pages in this dictionary look like: A, B
Math dictionary at http://mathdict.chitanka.info/en/de-en/ - this online dictionary has 3 languages: Bulgarian, German and English. I've learned about it from an answer to this question.
There also exists this English-Russian, Russian-English dictionary: Александров П.С.: Англо-русский словарь математических терминов 2 изд. Мир, 1994. Another Russian-English mathematical dictionary was mentioned in 042's answer.