Some words are MUCH more common than others, and it is useful to focus on their pronunciation.
The first 12 make up about 25% of all words.
The first 100 make up about 50% of all words.
The first 500 make up about 65% of all words.
However, if you read widely, then you will automatically come up against these words in these frequencies. Also, high frequency words tend to have limited content, and the low frequency words (mainly nouns and verbs) are the most important ones for meaning. This means you really need to develop general pronunciation techniques.
Further Reading:
A Frequency Dictionary of French (2009) Lonsdale, D., and LeBras, Y. Routledge: London. The book has 5,000 of the most common words, with translations, examples of their use, and thematic groupings. 4.5/5 on Amazon.
Now record your own voice and listen to the playback - check for any differences
Repeat until they sound the same
A powerful technique is to play the word/phrase, and to 'shadow' - say the word/phrase out loud at the same time as you listen to it. Do this a number of times (until you feel confident), then go straight on to record.
As soon as you think that you are able to copy accurately, record and listen to your own voice first, then only check if you feel you need to.
Once you get the main pronunciation right, try to get the overall rhythm and tonality the same as well. In French, the main word emphasis is usually on the last syllable of the last word in each phrase.
It can often be a good idea to try a tricky word/phrase in your head a few times, before recording.
The time available for you to make the recording is set at normal talking speed, plus a small amount extra. When you are fluent with the word you will not need all of this.
When you listen to the word/phrase, a translation is also briefly shown below the buttons. This is only there as a reminder for you to check if you wish.
The speed adjustment gives you three levels:
Slow - for starting out, and when you are having problems with particular sounds.
Normal - this is close to formal speeches and will be used when people know that you are not French.
Fast - this is close to normal, conversational French. It is worth aiming for this as it's a form of 'over-rehearsal'. When you can do something fast, then it becomes automatic and you're less likely to regress.
Incidentally, it does seem true that French is normally spoken 16% faster than English. This appears to be due to the fact that French has a lower informational density, so you need to talk faster to get the same information across (Pellegrino et al 2011).