using sharepoint designer workflow as a sequential

SharePoint designers are meant to be sequential workflows from 2007. But since you are usign SharePoint 2013 you can design state machine workflows also as you can use stages & go to statements.

 

Especially, the multiple level approval workflows can be created easily using designer. 

Approval workflows are State workflows, as they maintain state of the approval process. These can be easily created in SPD using "Start approval process" activity.

Please refer below article:

https://threewill.com/configure-sharepoint-approval-workflows-with-sharepoint-designer/