For the counter you can use 2 buttons (plus and minus) and an input field. Each button calls a microflow that does the +1/-1 of the value of the inputfield.
For the hide/unhide part of your question, you can use visibility for this: https://docs.mendix.com/studio/page-editor-widgets-visibility-section. Create a boolean in you data model, which is flipped using a microflow that is triggered by the button. You can then use this boolean to determine the visibility of an mage. Or the visibility of a container/tabs/input field etc.
I hope this helps.