How can I pray in my open shop, crowded with passersby, and should I pray standing or sitting?

Prayer is obligatory at its appointed time. If it is possible to pray standing in the shop because space is available, then do so, as standing is a pillar that is not waived except in cases of inability or unbearable hardship. If the shop is too cramped, then close it at prayer time and go to the nearest mosque or prayer area. If none is found, then every pure spot on earth is a mosque.