WebGL -Chrome seems to do nothing while loading WebGL appllication

Hello,

I'm creating a WebGL application allowing user to configure simple objects (couch, chair, etc...) I have done a first simple model of the application just to test/show it.

On Google Chrome the application needs about 13 seconds to be up. Comparing to all i have read, I agree this is not a lot but it is still too much : the application will run on commercial website and 13s is too much for a customer...

Opening the Chrome console it appears that during the loading process there are many times when chrome seems to do nothing. (more than 5 seconds in total ! You can see it in the screenshot joined with the post)

informations :

3d models, materials, textures, are dowloaded as asset bundles so they are not included in the build ; - it appears whit all compression format (gzip and Brotli) ; - enable exceptions is set to 'None' ; - strip engine code is disabled ;

Can someone explain me what are this 'empty times' correspondng to ?

Is there a way to remove them ?

Thank you in advance.

Ben.