German is most similar to other languages within the West Germanic language branch, including Afrikaans, Dutch, English, the Frisian languages, Low German, Luxembourgish, Scots, and Yiddish.
As part of a group of high German languages, Luxembourgish is the closest language to German—more closely related to standard German than some of the other high German dialects you'll hear in countries such as Austria and Switzerland.
The grammar of the German language is quite similar to that of the other Germanic languages.
The languages: Dutch and German
Dutch is very similar to German, especially with regards to vocabulary, but the grammar is very different. It could be argued that Dutch has developed further and has become more simplified. The difference between the two languages is very clear when you look at the four cases.
When it comes to vocabulary, German has more in common with English than Italian, due to the fact that they're both Germanic languages. Italian and German also use a different word order and sentence structure. Italian is similar to English in that they both have an SVO structure (subject-verb-object).
Except for Frisian, Dutch is linguistically the closest language to English, with both languages being part of the West Germanic linguistic family. This means many Dutch words are cognates with English (meaning they share the same linguistic roots), giving them similar spelling and pronunciation.
The closest language to English is one called Frisian, which is a Germanic language spoken by a small population of about 480,000 people. There are three separate dialects of the language, and it's only spoken at the southern fringes of the North Sea in the Netherlands and Germany.
Dutch, German, English, Swedish and Danish are all Germanic languages but the degree of mutual intelligibility between these languages differs. Danish and Swedish are the most mutually comprehensible, but German and Dutch are also mutually intelligible.
Although Dutch and German are related, it is very difficult for speakers of the two languages to understand each other.
Across multiple sources, Mandarin Chinese is the number one language listed as the most challenging to learn. The Defense Language Institute Foreign Language Center puts Mandarin in Category IV, which is the list of the most difficult languages to learn for English speakers.
What two languages are the most similar? Spanish and Portuguese are the most mutually understandable pair. In certain circumstances, television stations do not even translate between the two languages, presuming that Spanish-speaking viewers will understand Portuguese and vice versa.
Norwegian is closer to English than either Danish or Swedish. In fact, it's often described as the easiest of the three languages to learn.
Usually, the more educated people will speak with a British accent. The vowel sounds of German also sound more like the vowel sounds in British English, so I think most Germans lean slightly towards a British accent.
Upper Saxon Dialect (Sächsisch)
It is fairly similar linguistically to standard German and other dialects, but it has an accent that many German speakers have strong feelings about (like how many Brits dislike American accents).
French is a Romance language, and German (like English) belongs to the Germanic family. You also don't need a very highly trained ear to tell that they both sound very different. A French speaker would have a hard time understanding a German speaker, and vice versa.
Of these, Spanish and Italian are the easiest for native English speakers to learn, followed by Portuguese and finally French.
Mandarin (1,118 million speakers)
However, it's the most spoken language in the world if you count only first-language (native) speakers due to China's significant population. Mandarin is not actually a language, but a set of dialects of the Chinese language.
The etymology of Deutschland is pretty simple. The word deutsch comes from diutisc in Old High German, which means “of the people.” Land literally just means “land.” In other words, Deutschland basically means something to the effect of “the people's land.”
Afrikaans descended from Dutch dialects in the 17th century. It belongs to a West Germanic sub-group, the Low Franconian languages. Other West Germanic languages related to Afrikaans are German, English, the Frisian languages, and the unstandardised languages Low German and Yiddish.
When it comes to grammar, pronunciation, and vocabulary, German and Danish are very closely related. Indeed, Danish and German often seem to be more closely related than either one is to English. Both languages have gendered nouns, but German has three and Danish has two.
The Old English period is followed by Middle English (12th to 15th century), Early Modern English (c. 1480 to 1650) and finally Modern English (after 1650), and in Scotland Early Scots (before 1450), Middle Scots (c. 1450 to 1700) and Modern Scots (after 1700).
Closest Major Language: Dutch
Like Frisian and English, Dutch is another West Germanic language that developed from Proto-Germanic. Because of this, Dutch possesses many words and phrases similar to English and has a similar grammatical structure.
(Read H.L. Mencken's 1926 Britannica essay on American English.) Four dialects of the Old English language are known: Northumbrian in northern England and southeastern Scotland; Mercian in central England; Kentish in southeastern England; and West Saxon in southern and southwestern England.