So, a nasal voice - what to do about it?
Stand up straight with your back straight. Close the nostrils of your nose gently with two fingers. Don't exert too much effort so that you don't have trouble breathing. Leave yourself free to breathe. Say the words exclusively into your nose: "ONE-TWO-THREE-FOUR, ONE-TWO-THREE-FOUR."
And now, keeping your nose covered, say the same words, directing the sound to your front teeth.
Note that in the second pronunciation, you only hear the sonorous sounds in your nose. If you have no nasal sounds when pronouncing, then you are directing the air jet and your sound correctly.
Pronounce any phrases, alternating the direction of the sound: into your nose, then onto your teeth. If you are having trouble directing the sound to your teeth, try an auxiliary exercise.
Exhale air through your mouth while relaxing your lips. This movement is similar to exhaling a horse. Lightly and gently for 2-3 minutes, exhale through relaxed lips, making them vibrate. Another variation of the exercise, which will teach you to direct the sound and breath to your teeth, is to pronounce the words in an intentional manner, clearly highlighting each sound. This exercise is especially suitable for Slavic speakers. "PECHKA, CHASHKA, ONE-TWO-THREE."
Practice by changing the direction of the sound where you want it to go. Doing the exercise regularly will help you get rid of the nasty nasal sound. And may the power of voice design be with you.