Minha avó sempre torce a roupa à mão porque acha a secadora barulhenta.

Because avó is a feminine noun meaning grandmother. In Portuguese, possessives agree with the noun they describe, so you use:

• minha avó = my grandmother
• meu avô = my grandfather

So minha matches the feminine noun avó.

Here, torce comes from the verb torcer and means to wring or to twist clothes in order to remove water.

So torce a roupa à mão means something like:

• she wrings the clothes by hand
• she hand-wrings the laundry

This is a specific meaning of torcer. In other contexts, torcer can also mean:

• to twist
• to root for / cheer for a team

So context matters a lot.

In Portuguese, roupa is often used as a collective singular noun to mean clothes or laundry in a general sense.

So:

• lavar a roupa = to wash the clothes / do the laundry
• torcer a roupa = to wring the clothes / laundry

Even though English often uses a plural idea, Portuguese commonly uses singular roupa this way.

À mão means by hand.

So:

• torcer a roupa à mão = to wring the laundry by hand

You will see à mão in many common expressions:

• lavar à mão = to wash by hand
• fazer à mão = to make by hand
• escrever à mão = to write by hand

That à is a contraction of:

• a (a preposition)
• a (the feminine article)

This contraction is called crase.

In à mão, the expression is fixed, and Portuguese uses à with the grave accent. For learners, the easiest thing is to memorize à mão as a set phrase meaning by hand.

Portuguese often leaves out subject pronouns when the meaning is clear from the verb or the context.

In this sentence, the subject is already Minha avó, so repeating ela is unnecessary:

• Minha avó sempre torce a roupa à mão porque acha a secadora barulhenta.

This is very natural in Portuguese.

You could say:

• ...porque ela acha a secadora barulhenta

but it is usually less natural unless you want extra emphasis or contrast.

The verb achar can be used directly with a noun and an adjective to mean to find / consider something + adjective.

So:

• achar a secadora barulhenta = to think/find the dryer noisy

This pattern is very common:

• Acho o filme interessante. = I think the movie is interesting.
• Ela acha a casa pequena. = She thinks the house is small.

You could also say:

• acha que a secadora é barulhenta

That means essentially the same thing: she thinks that the dryer is noisy.

Because it describes a secadora, which is a feminine noun.

In Portuguese, adjectives usually agree in gender and number with the noun they describe:

• o secador barulhento = the noisy dryer (masculine)
• a secadora barulhenta = the noisy dryer (feminine)

So barulhenta matches secadora.

In Brazilian Portuguese:

• secadora usually means a clothes dryer
• secador often means a hair dryer

So in this sentence, a secadora clearly means the laundry machine used to dry clothes.

Adverbs like sempre often come before the main verb in Portuguese:

• Minha avó sempre torce...

This is the most natural placement here.

You may also hear different placements in some contexts, but subject + sempre + verb is a very common and useful pattern:

• Eu sempre estudo à noite.
• Ela sempre chega cedo.

Here porque means because, so the one-word form is correct:

• ...porque acha a secadora barulhenta = ...because she thinks the dryer is noisy

A very useful rule:

• porque = because
• por que = usually why / for what reason
• por quê = why at the end of a question
• porquê = the reason (a noun)

So this sentence needs porque because it introduces the reason.

Yes, it is natural and understandable. It means that she manually wrings out the laundry instead of using the dryer.

Depending on the region or situation, Brazilians might also say things like:

• torce a roupa na mão
• torce as roupas à mão

But torce a roupa à mão is perfectly natural and idiomatic.

You could say:

• Minha avó sempre torce as roupas à mão...

That would also be correct.

The difference is mostly one of style and nuance:

• a roupa often refers to laundry/clothes in general as a mass or collective idea
• as roupas refers more clearly to individual garments/clothes

In everyday Portuguese, both can work, but a roupa is very common when talking about laundry in general.