While we love all languages, English tends to get more of the spotlight at The Lingua File than other languages since it's our mother tongue. As our mother tongue, we didn't learn it in the same way as we did our second languages, so we have a vastly different understanding of it.
The first major difference we tend to find between English and our other languages is that, despite using English more fluently and with greater ease, we tend to understand significantly less about why we say certain things the way we do, having never studied them in the same depth as the rules we had to learn during foreign language tuition.
|An American cowboy in Dakota Territory in the 1880s.|
Take time prepositions for example. We say in the morning, in the afternoon, and in the evening. However, we say at night. Sure, in the night exists, but we would rarely say it. We just know that "night" is used differently. I'm sure these exceptions are incredibly frustrating for those who are learning the language.
When you consider prepositions in general, the same type of exceptions that irk learners concerning time prepositions also occur with other prepositions, and can result in a lot of frustration when learners have to tackle them.
And what about pronunciation? For users of languages with a phonemic orthography (a language whose written symbols correspond directly to a given sound), English must be incredibly annoying. Why does the "u" sound different in unite and untie? They look almost identical to one another...
Don't forget phrasal verbs, too! They are so annoying for those learning English as a second language that we even dedicated an entire post to it!