Convert to vantage-child mess

Hi,

Discovering WordPress during this fall, I choose Vantage theme to built a new website for my biking, hiking club Cyclo-Nature. I use this address as a developper website.
http://cyclonat.pmenard.profweb.ca
In my learning curve, I realised that It’s better to work with a child theme. So I try to convert vantage to vantage-child. I follow the procedure given on SiteOrigin Site. Result in a messy interface. I clone the good copy of my site and redo all the customisation on my child site using my parent site as model. Many things went correct, but some mess persist:

– Menu item is just a plain vertical list
– Sidebar stay at the bottom of the page, even If I ask to go left, or right

I remove all the extension and I still got messy menu item and rebel sidebar
Any hint on what to do next ?
I wish I will not had to redo the whole process and built a child theme before doing any customisation or write post, page or event.
Thanks for your time.
Pierre