Build VPN Android App from Scratch OR fix existing app's issues

We are looking for an Experienced android developer to develop a VPN app from scratch. We already develop a VPN app from scratch but sometimes we faced connection issues (like DNS_PROBE_STARTED, DNS_PROBE_FINISHED_NO_INTERNET) and speed issues. App link: https://play.google.com/store/apps/details?id=com.worldwide.vpn.fast.proxy.tools

We are looking for an expert who can resolve those issues from the existing VPN app OR develop a new VPN app from scratch.