> I will never be able to pronounce correctly a word I never heard before.
This happens not infrequently to native English speakers. It's especially prominent for people who read a lot when they're young and develop a large vocabulary that doesn't get socialized until much later. My English teacher, of all people, was notorious for this.
Real life examples from native speakers: Emphasizing the wrong syllable in "forage", "respite", and "parameter". Pronouncing "draught" like "fraught". Softening "chasm" and "chaos". And an extra syllable (long e sound) in "homogeneous".
This is my experience as well. I would just add
> Emphasizing the wrong syllable
As a native French speaker, I will never be able to emphasise the right syllable in any language, ever :D
Stress is just not really a thing in French, and it is quite difficult to get it intuitively later in life.
It's fairly easy when the stress is consistent or mostly so. In English thought it's a phonemic feature in its own right so there's no general rule to memorize in the first place - you just have to learn it for each word.
It is not that different from English in that respect. I found both to be quite difficult compared to e.g. German, which is very regular, or Spanish (which is annoying grammar-wise but straightforward to pronounce).
Spoken English is full of elisions and silent letters, and also full of locale-dependent colloquialisms that take some time getting used to. I remember struggling for a while living in New York and London despite having a decent level in “standard” English. I still occasionally struggle with my mates from Ireland and Yorkshire. After living more than a decade in English-speaking countries I accepted that I will never be able to pronounce correctly a word I never heard before.
Missing liaisons is not problematic when you speak French. It marks you as a non-native but it does not make you harder to understand. They can be often omitted by natives as well, depending on the accent.