What do you mean with "hacking"? Are you using the official client download from the Download section of this site?
If no, change forum
If yes, well. Teeworlds, like every other name, can't be every time smooth for 3 motivations:
- connectivity: lags based on you internet connection. If it's that check your ping (80 should be considered good) and then, if it's high, ask your provider why or stop downloads
- hardware: this game haven't so much requirements. By the way, if you system is really old, you should experience hardware lags on high quality and resolution. Simply try to slow down them in your config.
- software: maybe you missed installing the right drivers for your VGA / motherboard / LAN / Wireless LAN. If it's that, download and install them from your hardware retailer.
I realised you said expecially when moving fast. Try to enable the vsync in the options.
Support Staff - ESL.eu Teeworlds Admin