Howdy!
1. About the PHP error: What should i do to remove that notice? You know i am not a coder.
You would want to either stop using the GW Go Pricing
plugin, or contact the support team for the plugin to help get that issue fixed.
2. Button Frozen: With some products i use a plugin which redirecting to amazon but some products i add manualy by woocommerce plugin still not proceed by paypal or 2checkout. The button is frozen. You can see the link below:
Link Product 1
The button is frozen
I see what you mean now, as the Your Order
section is grayed out and inaccessible:

Link to image: https://cld.wthms.co/0Yctox
This kind of problem is usually caused by either a conflict with your theme or with another plugin.
?
The best way to determine this is to:
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- Temporarily switch your theme to Storefront
- Disable all plugins except for WooCommerce
- Repeat the action that is causing the problem
If you’re not seeing the same problem after completing the conflict test, then you know the problem was with the plugins and/or theme you deactivated. To figure out which plugin is causing the problem, reactivate your other plugins one by one, testing after each, until you find the one causing conflict. You can find a more detailed explanation on how to do a conflict test here.
When you have all plugins deactivated and switch themes, if that doesn’t help it work, please also check to see if these issues still display:

Link to image: https://cld.wthms.co/gZPtC7