Cannot apply operator * to types Text and Number

Hi all,

I try to do below formulation but still getting error.

Step I already try

1. if[#"SAP_MMT_LV_MKPF_EN.D/C_SHKZG"]="H" then Value.Multiply([Quantity_MENGE],-1) else [Quantity_MENGE]

2. if[#"SAP_MMT_LV_MKPF_EN.D/C_SHKZG"]="H" then [Quantity_MENGE]*(-1) else [Quantity_MENGE]

3. I change the data type for [Quantity_MENGE] from number to text

Regards,

Nuha