I usually buy things online because it's very convenient and the prices are lower than buying them in physical stores. I usually buy things online because it's very convenient and the prices are lower than buying them in physical stores.

Alternatively: "...because it's very convenient and it's cheaper than buying them..."

I usually buy things online because it's very convenient and the prices are lower than buying them in physical stores. Or try "... and the prices are lower than they are in physical stores" in order to balance the comparison (prices online are lower than prices in physical stores). The implicit subject of "buying" (I) is not what you are comparing. I'm only saying this because you are *so* advanced and I am offering some comments for you to consider. I usually buy things online because it's very convenient and the prices are lower than buying them in physical stores. Or try "... and the prices are lower than they are in physical stores" in order to balance the comparison (prices online are lower than prices in physical stores). The implicit subject of "buying" (I) is not what you are comparing. I'm only saying this because you are *so* advanced and I am offering some comments for you to consider.

But it also has some disadvantages. I recommend defining the "it" as subject, such as "But online shopping also has some disadvantages." More formally: "However, online shopping has its disadvantages." For formal writing, "but" is a coordinating conjunction and "however" is an adverbial conjunction. In formal or academic writing, we usually avoid using coordinating conjunctions to start sentences. But it also has some disadvantages. I recommend defining the "it" as subject, such as "But online shopping also has some disadvantages." More formally: "However, online shopping has its disadvantages." For formal writing, "but" is a coordinating conjunction and "however" is an adverbial conjunction. In formal or academic writing, we usually avoid using coordinating conjunctions to start sentences.

There's also a risk of buying fakes, and the goods I've received may not live up to my expectations. There's also a risk of buying fakes, and the goods I've received may not live up to my expectations.

There's also a risk of buying fakes, and the goods I received may not live up to my expectations. I think you mean the habitual present here: "... the good I receive ..." There's also a risk of buying fakes, and the goods I received may not live up to my expectations. I think you mean the habitual present here: "... the good I receive ..."