Explode - Polyline

Home tab > Draw panel > Explode

Select the polyline

Press Enter

Polyline seperate into lines and arcs

Join lines and arcs into Polyline

Start Polyline Edit command

Command line: Multiple

Cross-select all objects

Press Enter to confirm the convertion

Select Join

Press Enter if there is no gap in between

Lines and arcs convert to polyline and join into one polyline