English has only 26 written letters but there are more than 40 sounds in English. Tip one is to learn the sounds of English. Once you know the sounds you will find it easier to speak.
What are the sounds of English?
The Phonemic Chart
There are many easy to use apps to help you learn the sounds of English. Download an app for example, Sounds: The Pronunciation App by Macmillan and you can start improving today. There are plenty of other apps available so keep trying until you find the right one for you.
Now use your app to start improving.