is this even possible?

So a couple weeks ago i changed my theme and optimize page speed a lil bit and suddenly my bounce rate drop from avg 50% to avg 2%
i mean is this even possible or theres something wrong with the code?is there anybody with the same experience?

You gotta tell us more. As there can be many contributing factors to it.

STEP 1 - CACHING PLUGIN
The plugin W3 Total Cache will cache and compress a load of files to reduce page download time.
Log into WordPress as admin
Plugins -> Add New -> Search ‘total cache' -> Install ‘W3 Total Cache'
Plugins -> Activate W3 Total Cache
Under the new ‘Performance' menu -> General Settings -> Select the following:
Enable ‘Page cache'
Enable ‘Minifiy' (keep default settings)
Enable ‘Browser cache'
Click any ‘save all settings' button
Select ‘Empty the page cache' notification if it appears at the top of the page
Double check your WordPress site/blog to make sure everything is working

STEP 2 - .HTACCESS MODICATION (APACHE SERVER ONLY)
Modifying the .htaccess file to tell the browser to cache and compress various files to reduce server load and improve page speed performance.
FTP Download the .htaccess file from the root of your WordPress site
Open the .htaccess file using your favourite text editor
Copy and paste the below code at the end of the file and re-upload
##### EXPIRE CACHING - LEVERAGE BROWSER CACHING #####

# Enable expirations
ExpiresActive On

# Set default expire time
ExpiresDefault "access 2 week"

# Specify expire time by file type
ExpiresByType image/jpg "access 1 month"
ExpiresByType image/jpeg "access 1 month"
ExpiresByType image/gif "access 1 month"
ExpiresByType image/png "access 1 month"
ExpiresByType text/css "access 1 month"
ExpiresByType application/pdf "access 1 month"
ExpiresByType text/x-javascript "access 1 month"
ExpiresByType image/x-icon "access 1 month"