General stuff to be aware of as an English language learner
English spelling and pronunciation have a complicated relationship. It's normal to not be able to derive the pronunciation of a word from the spelling. There are a lot of useful rules that can allow you to make an educated guess, but there's no guarantee that the actual pronunciation will follow these rules. It might be an exception. The only way to be confident a pronunciation is correct is to check a good pronouncing dictionary, such as the Longman Pronunciation Dictionary. (If you don't have one of these, there are many free online dictionaries that list pronunciation; a good resource for accessing these is the OneLook Dictionary Search). Make sure the dictionary transcriptions are in the accent that you're trying to learn.
More specific information about the spelling of tomb
It's normal for the spelling mb at the end of a word to correspond to /m/: other words like this are jamb, lamb, plumb, dumb, climb, limb.
There are also a number of other words in English where a single o represents the /uː/ sound normally associated with the digraph oo: womb, who, whom, two, to, do, lose, prove, move. This is "irregular," but it is a pattern rather than an isolated occurrence.
So it's true the spelling is unusual and irregular, but if we break it up into parts we can see patterns that occur in the spelling of other words.
In this answer, I've tried to explain the pronunciation and spelling of tomb by comparing it to other words in Modern English, rather than by tracing its historical development. The historical development of a word's spelling and pronunciation can be pretty complicated, and it's usually not useful information for learning English. If you're interested in this subject anyway, I've written an answer that focuses on that historical side of things on the English Language and Usage site: Why do “bomb” and “tomb” have different pronunciations?
"Right" and "Write" are both pronounced as [raɪt]. There is no difference in pronunciation by grammar defaults, however, depending on the dialect it may slightly vary.
Concerning your additional question, two things should be cleared out:
- Try to be as clear as possible and try to sound lucid so anybody can understand the words you speak.
- Try to bring in some British or American accent into your voice little by little without ruining your clarity.
I, myself, am not a native speaker but I always try to copy people who speak fluently and with clarity. I especially love book reader. Their voice and clarity is almost always amazing.
Best Answer
𝑇𝐿;𝐷𝑅
In General American English, don't is pronounced /doʊnt/ while in Southern Standard British English, it's pronounced /dəʊnt/.
In don't you, the /t/ of don't and /j/ of you coalesce to /tʃ/. The process is called assimilation.
𝐸𝑥𝑝𝑙𝑎𝑛𝑎𝑡𝑖𝑜𝑛
Assimilation makes nearby sounds more similar to each other. The kind of assimilation in don't you is called coalescent assimilation.
When /j/ comes right after /t/, there's a tendency to assimilate them to /t͡ʃ/. The /t/ is normally articulated at the ridge right behind the top teeth (alveolar ridge), but when it comes before a /j/ (which is articulated further back in the mouth—at the hard palate), it's usually pronounced /t͡ʃ/. What happens here is that the /t/ is articulated further back in the mouth in anticipation of the following /j/, so it becomes /t͡ʃ/ i.e. they coalesce to /t͡ʃ/.
The following sounds often coalesce:
You might have noticed that in informal situations (mostly in chatting platforms), most people write contractions such as dontcha, whatcha, gotcha etc. These are the phonetic spellings of the assimilated forms.
Similarly, 'did you' is often pronounced as /dɪdʒjuː/ because /d/ and /j/ assimilate to /d͡ʒ/.
No. It's not restricted to American English.