I am using the "Minimal" theme and every time my customers add something to their cart they get redirected to checkout. Instead I would like them to either be given an option to checkout or continue shopping, or to be redirected to one of my collections. Is there also a way to implement an add to cart button when an item is displayed on my collection page?
I tried your site adding to cart takes you to /cart as it should but your post implies https://checkout.shopify.com
duplicate your theme->in duplicate theme edit html/css -> in product.liquid find this line
<input type="submit" id="add-to-cart" class="btn" name="add" value="Add to cart">
below that paste
<input type="hidden" name="return_to" value="/collections/" />
Save, Preview and test duplicate theme
change value="/collections/" to what you want for all products or use liquid and logic to generate the proper url fragment for each product.
Publish theme when satisfied.
As for cart buttons on collection pages that is a separate topic you should search forums for, then create a new one if you don't find a method for you.