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)