Can someone help me with this Minecraft command?
Solution 1:
The syntax of /scoreboard players tag is:
/scoreboard players tag <player> <add|remove|list> <tagName> [dataTag]
You are missing add before flowerpot.
SelectedItem should be a compound tag (curly brackets) rather than a list (square brackets).
There's also some other issues with your closing brackets, such as trying to close Lore:[ with } rather than ].
The fixed command should be:
/scoreboard players tag @a add flowerpot {SelectedItem:{id:"minecraft:flower_pot",tag:{display:{Lore:["Işınlayan Saksı"]}}}}