Tengo una fiebre muy alta
fiebre reumatica (accent on the first 'a' in 'reumatica')
You say, ¿Cuán alto?
La escuela secundaria is high school in Spanish. Spanish(Mexico): Preparatoria
No muy buena is the best way to say "not very good" in Spanish.
98.6F is normal but anything above 100F is high but could be due to running, etc. A fever would be anything above 100F. A virus would cause this or a bacteria would produce a higher fever 102F and above.
Very similar in spanish: Mascota
Say "Muy delicioso!" (Very dilicious.)
hola = hi! alto/a = high
The phrase "high and low" in Spanish is "alta y baja" (high in extent or value is máximo).
buena vida
volumen alto
alta temperatura