This is a demo tutorial. While there is no step-by-step commentary available (yet), the live demo below is fully functional. Feel free to open it for full source code.
This demo shows how horizontal axis can be placed into a different container so it remains static and visible when oversized chart is getting scrolled.
See the Pen amCharts 4: Freeze horizontal axis by amCharts team (@amcharts) on CodePen.24419