One way to insert a line chart into PowerPoint is to create the chart in Excel and copy it, keeping a link to the original, if you want.
Copy an Excel chart
If your data is complex or you plan to update it frequently, create the chart in Excel, and copy it into PowerPoint. Here’s how:
In Excel, click the chart that you want to copy to another Office program, and press Ctrl+C.
Open PowerPoint, click where you want to paste the chart, and press Ctrl+V.
Click Paste Options next to the chart, and choose how you want to paste the chart. For more information about the different options you can choose from, see Copy an Excel chart to another Office program.