- En unos pocos minutos tendré que dormir.

- Enseguida cuanto termine la película termina, tendré que volver a casa.

We also have expressions such as "Tan pronto como [verb in subjunctive]" and "Inmediatamente después de que [verb in subjunctive]

- Hoy en día, la gente no hablase en trealidad sí en la vida real.

I would say "entre sí" is probably redundant here because "gente" is a group of people, but I put it in there because the English has "each other"

- Jamás diré esto.

Esto = This
Eso = That

- Recién volvíEn cuanto llegué a casa, comí comida.

We rarely say "comer comida". It is perfectly fine to say that in English, but it is rather cacophonic in Spanish... and your closest friends might reply with the obligatory joke, "What else are you gonna eat?" :)

- Una vez más qQuiero celebrar una vez más.

This word order is more natural.

- La tienda está adelante de mi casa.

"Adelante" implies movement. Saying "delante" is correct, but generally is used in situations where there's some sort of alignment (such as a line in the supermarket, or a position on a waiting list). I would say in this case the most common expression would be "enfrente de mi casa". This latter expression implies that the store is directly opposite to the front of the house.

- ¡Ahí está ella!

This is grammatically correct. If you know by context that it's a she, you can drop ella and just say "¡Ahí está!

- Caminé alrededpor mi barrio.

- ¡Ella está atrás/detrás de ti!

"detrás" is the correct one here.

- Su casa es a travéstá al otro lado del río.

- Tienes que ir a travésbajo la lluevevia.

Not sure here. If you're walking, we would say "bajo la lluvia", but not sure what we would say if you were driving a car.

- Su casa está enfrente de la míoa.

Casa is feminine, so it should be "mía"