Hallo. My name is Redlightning and I want to work with my voice. But I have a problem with Audacity. I recorded a video about this problem, here is URL:
https://www.youtube.com/watch?v=3yIEM8A2o8U&t=4s
In words. I press “Record” and recorded any sentence. Then I will go to start and press “Record” again, recording another sentence. And then I press “Play” …Now is the problem.
When I press play, each sentence is understandable.
I did not had this problem 1 year ago. From that moment I still have this problem
Can you help me with this problem? I really need your help. Work with voice is what I really want to do and this is slowing me down
SORRY FOR MY ENGLISH!!! 
OS: Windows 7
HW of my notebook: https://gyazo.com/6250a33bc494da6f0dce07186692845f 3GB RAM
Thank you for every read and have a really nice day!! 
I think I got it. Your microphone or microphone system is producing a “DC Offset” error. A bad one.
Look on the left of the blue waves. The waves are supposed to start and end at 0.0 like my picture.

You can fix this temporarily.
– Select one whole clip or show by clicking just above MUTE.
– Effect > Normalize: [X]Remove DC > OK
Now do it to the other track. That should return the tracks to normal and they should both play at the same time.
You will have to do this correction every time you press Record. So your microphone is broken and you should fix it before you do any more work.
Koz
Koz you are the GOD!! Thank you thank you thank you! You are the best!
Problem is solved. It was really that problem. I don’t know, how to shut it down pernamently, but this really helped me.
THANK YOU! 
I don’t know, how to shut it down pernamently
It’s pretty serious. You usually have to repair or replace the digitizer. If you’re using a USB microphone (Blue Snowball) it’s inside the microphone. If you’re using a USB sound mixer, the digitizer inside the mixer may be bad.
It can get worse. If you’re using an analog microphone plugged into the side of your computer, the digitizer inside the computer may be fried.
There are more wacky possibilities. The computer may be bad and all your USB devices are acting funny but you only noticed the microphone. Would you notice if your USB mouse skipped a little bit? Your USB keyboard missed a key here and there?
Koz
I use headset, so mic is on Jack 3.5
No, my USB is in good shape. Next week I am gonna buy NEW PC, so I will try on it 
Thank you for your help