Hi, I tried with MSTL having seasonality 364, 30, and 7, which captured the overall seasonality quite well, but performed very poorly with promotion shifts. For example, this year black friday promo started two days earlier leading to 20x sales vs non promo day last year. Even when adding hotcoded exogenous variable indicating promotion type, the model more or less predicted similar pattern as last year. Maybe I should explore mlforecast lightgbm etc. if it could capture the promotion impact better. Also, if someone has good tips for beginner would be more than glad to hear :)