how to overcome problems in pronouncing consonants?

I'm from Vietnam. I often substitute some English consonants with similar Vietnamese sounds. How can I overcome this problem?
Furthermore, I also have difficulties with final consonants and consonant clusters. I often omit them or add an extra vowel. What should I do?
Finally, could you tell me how to practise using linking and assimilation?
Thank you!!!

[blacknomi]

So I guess you type like this but talka(schwa) lika(schwa) thata(schwa)?

Read it slowly.

Rea dit slow-ly.

[Tdol]

Blacknomi's right- connect by merging words instead of adding vowels. We add consonants- law & order, but not by adding vowels much.