Some have said that English is the hardest language to learn. Do you think that's really true?

NO.   Mandarin is really hard.

Phonology

The initials of Sin Sukchu's standard readings (mid-15th century) differed from those of Late Middle Chinese only in the merger of two series of retroflexes:[20]
Labials p pʰ b m f v ʋ
Coronals t tʰ d n l
Sibilants ts tsʰ dz s z
Retroflexes tʂ tʂʰ dʐ ʂ ʐ r
Gutturals k kʰ ɡ ŋ x ɣ ʔ
Zero ∅

Sin's system had fewer finals than Late Middle Chinese. In particular, final stops -p, -t and -k had all merged as a final glottal stop, as found in modern Jiang-Huai Mandarin:[21]
əj əw əm ən əjŋ əʔ əjʔ
ɿ
ʅ ʅʔ
i iw im in iŋ iʔ
u uj un uŋ ujŋ uʔ ujʔ
y yn juŋ jujŋ yʔ yjʔ
ɔ ɔn ɔʔ
je jej jew jem jen jeʔ
wɔ wɔn wɔʔ
ye yen yeʔ
a aj aw am an aŋ aʔ awʔ
ja jaj jaw jam jan jaŋ jaʔ jawʔ
wa waj wan waŋ waʔ wawʔ

This system had mid vowels [e] and [ɔ], which have merged with the open vowel [a] in the modern standard language. For example, 官 and 關 are both guān in the modern language, but were distinguished as [kwɔn] and [kwan] in Sin's system.[22] The Middle Chinese level tone had split into two registers conditioned by voicing of the initial, as in modern Mandarin dialects.[22]

In comparison with Sin's standard readings, the major changes in the late Ming language described by European missionaries were the loss of the voiced initials and the merger of [-m] finals with [-n].[23] The initials [ʋ-] and [r-] had become voiced fricatives [v-] and [ʐ-] respectively.[24] [ʔ-] had merged into [ŋ-] before mid and low vowels, and both initials had disappeared before high vowels.[25] By the early 18th century, the mid vowel [e]/[ɔ] had merged with [a].[26] However unlike the contemporary Beijing pronunciation, early 19th century Mandarin still distinguished between palatalized velars and dental affricates, the source of the spellings "Peking" and "Tientsin" for modern "Beijing" and "Tianjin".[27]
Vocabulary This post was edited by WM BARR . =ABSOLUTE TRASH at August 19, 2017 8:59 AM MDT

That is what my grandmother says. She is Russian and had to learn how to speak ENglish. She said it was the most difficult language to learn because it consisted of alot of different languages put together. She spoke a little Chinese and Polish too. 

Well, I wouldn't know considering English was my first language. Obviously it seems easy to me if I already knew it.

for me it wasnt, i was born in south america and came to nyc when i was 7 and had to learn english then, guess its easier if youre younger