Nav on footer part (blog page)

Hello, First: When I use the blog page to see the post, the nav menu is on the footer. How is possible to have the same on the top as it is if I select a post inside a widget http://fredericvoyage.fr/en/the-blog/ ANd the nav as I would want : http://fredericvoyage.fr/en/douro-valley-porto-portugal-march-2019/ If I have the nav on top and bottom, it's still okay Second: How could I put "Previous" on the left and let "Next" on the right. Thank you very much for your help Frederic