This code opens the shop when someone else steps on it.. please explain to me how to fix this??

this code opens the shop when someone touches the shop, please help me fix this Code:

local guiname="Shop"
local Players=game:GetService"Players"
local function showgui(player,guiname)
	player.PlayerGui[guiname].Shop.PetInventory.Visible=true
end
local a;workspace.ShopPart.Touched:Connect(function(part)
	if a then return end;a=true
	local player=Players:GetPlayerFromCharacter(part.Parent)
	if player then
		pcall(showgui,player,guiname)
	end
	wait(1)a=false
end)