1. This should be helpful: http://www.jeremycarter.com.au/optimising-woocommerce-checkout-for-mobile/
2. If the setting is jumping back to global when you save, this should help: http://generatepress.com/forums/topic/hiding-page-title-on-homepage/#post-66701
3. I’ll have to look into this a bit more – I believe this would require altering WooCommerce files which I wouldn’t want to do by default in GP, but it may be possible to change it. I’m assuming the “Weiter” button is the purchase button?