1) Go to Boost'English - "Learning focus"- "voicework" (the 7 modules will make it all clear).
2) Train on the 200 tricky words: : https://h5p.org/node/470966
The Sciences Po IEP English dept. has recorded for you a specially designed set of audio files to train on the 200 words IEP students usually find tricky!
(You can download the Sciences Po pronunciation guide which will help you to identify and pronounce the stressed syllable, and then LISTEN AND REPEAT). You can choose to copy the UK or US accent...it's up to you!
There is a PERFECT RECORDING OF THE 200 WORDS by an IEP student in the files below.
RECOMMENDATION: You could download the free app AUDACITY to record your voice and listen to the sounds.
Plus, this site helps you pronounce reduced syllables better...http://www.trainyouraccent.com/
3) If you really want to get good, do some shadowing - watch the explanatory video and listen to the student example below.
4) Check how to pronounce individual words with https://howjsay.com/