no heat

Clean out the heater core by reverse flushing it. YouTube. It is easy

i tried to youtube but i cant find the heater core or idk what it looks like, felt the hoses and one of them is cold

Heater core is in dash Servicing is done in engine bay. YouTube. Heater core flush

If one of your radiator hoses is cold, it is a sign that your thermostat is not opening and allowing coolant to flow past it into the radiator. "Stronger" antifreeze will do nothing but change the boiling point of the coolant. Since your thermostat was changed, I would check that it is functioning and that it was put in in the correct direction (if it is backwards, it will not open properly).

A possible probem if this vehicle has injested crushed leaves . This creafes a film on the heatercore .remove core wash or replace core...