[rahimnathwani]

The same happens with foreigners learning Mandarin Chinese. The consonants are easy, but each vowel can be pronounced with one of 4 different tones (or 5 if you count the 'neutral' tone).

If you get a tone wrong, sometimes people will understand the erroneous word due to surrounding context. But pretty often you'll just elicit a blank stare. This is especially the case for short phrases, e.g. when you're asking for directions.

[chalcolithic]

>The consonants are easy

I wish. My teachers have no problem telling apart my j and q, but I rarely hear the difference despite all the cosonants in my native language coming in palatalized/non-palatalized pairs.

[rahimnathwani]

I forgot that English speakers often have difficulty with these pairs of consonant sounds in Mandarin:

j / zh

q / ch (the former is further forward in the mouth than 'ch' in English, and the latter further back, with a fully clenched mouth)