Why am I pronouncing words wrongly after practicing for many months?

An important part of pronunciation is the correct position of the tongue, that's why many people cannot master the proper pronunciation. It is through challenging and may take many weeks to get used to.

There are four tones in Chinese Mandarin. So we need to learn the tones pronunciation first just like on the notation, because in Chineses with different tones can be indicate different word while you express the wrong meaning; the rule for the tone sandhi should be known when you practice Chinese; more listening will be also the effective way to help you pratice correctly.

the frist thing you need to know , you can read every tones right, after that pratice more, read more and slow down. don't rush