Will plantar fasciitis be incredibly painful the first day i have it? will the pain go down?

Probably up, sorry: Pf can come on over time or abruptly, and tends to worsen over time without intervention to improve / address the circumstances that brought it about. Can try over the counter gel heel cup or similar insert, but may need to see podiatrist for orthotic or other assistance.

It could be: And i hope so, ice it , rest it, support it with an arch support.

Fascitis : Plantar fascitis typically you have severe pain to heel area getting out of bed and after sitting a while. Try rest, ice, stretching the foot toward your body, anti inflatory medication and cortisone injection. Orthotics will help it as well. Shock wave therapy could help but not covered by insurance same for prp injections.