The simple answer is actually, yes. You will lose speed. This is because when you connect to your target website through a VPN server you are not going directly to your target destination.
For example, if you want to browse a specific website in another country such as Germany without using a VPN, the connection request goes directly from your device wherever you are located to the website’s server Germany. If you connect via a VPN server located somewhere else, the extra hop in the journey of your request will invariably lose some of the original speed.