Título: Mis examenes pasadoanteriores con la gripe/congestionada/resfriada

con la gripe sounds a bit odd, bc it sounds like it's the title of a book? You can also say congestionada/resfriada, it's much more natural this way :) Also, anteriores and pasados are interchangeable, but here it sounds better to use the former :)

Acabao de leer tu correo que escribiste (en) la semana pasadoa.

Semana is a femenine noun :) Ex: La semana pasada visité a mi amiga" :)
Acaba vs Acabo:
When you end a verb with -a (For example: Camina, correrá, trabajará, va) it means you're talking about somebody else :) (Ella camina, él correrá) but when you want to talk about yourself, you put an -o (Acabo de leer, Voy a cocinar, yo corro, yo trabajo/trabajaré) :)

Espero que jyo y tu no tenegamos la gripe en este año.

when you want to express that something won't happen to you, use -amos or -emos :) "Espero que no perdamos, espero que no cerremos nuestro negocio" :)

MiEl semestre pasado estabauvo horrible porque de la gripe.

Estaba (Pretérito Imperfecto or PI) vs estuvo (Pretérito Indefinido or PID): The Pretérito Imperfecto (I'm going to call it PI from now on) can be used in many different situations, but mostly it's used when you're talking about something that happened somewhere in the past, that might still be taking place today, but it's never specified. (Example: Mi abuela estaba en su casa (she was at her home sometime in the past but we don't know if she might be there yet or not))
And when you use the Pretérito Indefinido (or PID from now on) you're talking about something that took place in the past and isn't happening right now. For example: Ayer estuve con mi amiga. Ayer estuve cocinando (All of which aren't happening right now) :)

No puedíde ni estudiar oni hacer mis deberes nada.

Here I'm trying to express the meaning you wanted to give with "nada". When you put "ni" before the verb/noun, you're emphasizing the fact that you couldn't do those things, and it sounds like you're a bit upset about it :) "Anoche no pude ni dormir ni descansar"

Repercutió mis grado muchoucho en mis notas.

Usually you add the word that intensifies the meaning (mucho, poco, bastante, etc) after the verb, this way it sounds much more natural :) For example, saying "Anoche dormí mucho" y "dormí mucho anoche" are both grammatically correct, but depending on the context the former might sound a bit literary :)

Hice mal a el exaámene de las matematicas.

The difference here would be:
Las matemáticas: It includes anything that's related to math. It sounds more like the title/subtitle of a book :)
(exámen de) matemática: perfectly fine, you're talking about math as a subject :)

Por lesta razón/Por eso, tengo que hacer mi mejor esfuerzo en el poróximo exaámen.

Si estudio mucho ahora, mis gradonotas va a estar bien.

Forgot to mention: grados are mostly used when talking about temperature or in which year of school you are (as in "I'm a sophomore, etc)

TDe todos modos, espero que estés bien y saludable.