If you’re serious then;
Remove and bin all carpets and curtains, in fact all soft furnishings. Leave windows opens as much as possible.
Sugar soap all walls and ceilings, clean house using bicarbonate of soda and warm water. Leave windows opens as much as possible.
Remove all dust and debris, Leave windows opens as much as possible.
Clean kitchen/bathrooms with white vinegar and then with bicarbonate of soda and warm water
Apply 2 – 3 coats of good quality paints to all wall/ceilings and gloss all woodwork. Leave windows opens as much as possible.
New carpets and leave windows opens as much as possible.
That should fix it
Else you could buy some miracle smell masking product