Hello, welcome to Bubble!
Bubble’s responsive engine is actually a great and simple tool for building responsively . Here are a few tips I use in my own projects that might help you:
1- Container Layout: The page container layout is typically set to Column, meaning all content (subgroups) will be stacked vertically.
2- Group Layouts: When adding elements within groups, think about their arrangement. For example, if two buttons should appear side by side, use Row layout. If they should be stacked, use Column.
3- Spacing & Gaps: Use the Gap spacing feature instead of manually adding empty elements or margins. This ensures consistent spacing between elements within a group.
4- To optimize for different screen sizes (mobile, tablet, etc.), use conditionals to adjust properties like font size, margins, and padding dynamically.
5- Only use fixed widths/heights for elements that should not change with screen size (e.g., buttons). Other elements should have min/max width and height to adapt smoothly.
6- To ensure images look great across devices, store them in Option Sets and retrieve them dynamically using ‘Get an option’. Additionally, use the Imgx processing action for better rendering and optimization.
Let me know if any of these tips help! Feel free to ask any questions or even schedule a quick 30-minute call together to take a look at your app and assist you with its responsiveness 
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