SCP-XXXX-1 is to be regularly treated and maintained for by Foundation medical personnel
I would suggest modifying this to be more clear. Specifically, something like;
"SCP-XXXX-1 is to receive regular care and treatment by foundation medical personnel"
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No other living matter is to be near nor make contact with SCP-XXXX-2.
For clarity's sake i would suggest changing this to read;
"SCP-XXXX-2 should at no time be put into contact with living beings other than SCP-XXXX-1 ."
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treating it in a manner similar to a pet, and attempts to care for it as such.
"…treating it in a manner similar to a pet, and attempting to care for it as such."
Would be a more consistent phrasing.
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SCP-XXXX-2 is the hair that grows from the head of SCP-XXXX-1, measuring up to approximately 1.9 m long, although it has been known to reach longer lengths by will.
This is a bit convoluted. I would suggest that you edit it to make your intent clearer. Does the hair only grow up to 1.9m long, or is that its base length? If the intent is that it remain at 1.9m normally, but can "reach longer lengths at will' I would change the phrasing to reflect that.
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SCP-XXXX-2 has shown to
"has been shown to."
Minor edit but important for clarity.
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and has even shown to have a predatory and animal-like nature.
I'm not a big fan of repetitive phrasing, so I would suggest changing this to something like;
"and has even demonstrated behavioral characteristics consistent with predatory animals."
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Microscopic examination of a strand of SCP-XXXX-2 has revealed hair-like structures that secrete a substance which, upon analysis, appears to be similar to gastric acid.
Ok, this is a little confusing, does the hair have hair? Is that what this is saying? The acid part sounds suitably clinical, but I am somewhat confused by the sentence structure here.
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When SCP-XXXX-2 detects any organic matter nearby, it will attempt to reach out towards the organic object and begin wrapping and coiling itself around it.
There is a bit too much repetition of the term 'it' here, which makes deciphering the meaning behind the sentence a process plagued by ambiguity.
If I understand correctly what you are going for, i would suggest changing this sentence to;
"When SCP-XXXX-2 detects organic matter excluding SCP-XXXX-1, it will attempt to reach and ensnare the organic object. Should it make contact, SCP-XXXX-2 will attempt to coil around, and eventually encase its target."
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it will then begin to pull the object towards itself and will continue doing so until it has reached the main body, then the object shall appear to descend and disappear into SCP-XXXX-2. No trace of the object is left behind after the process is completed.
This passage, while not strictly speaking grammatically incorrect, is extremely awkward to read. I would suggest the institution of a more streamlined structure. For instance;
"it will begin to draw the object towards SCP-XXXX-1's center of mass. If it is able to draw its target in to this degree, it will begin to completely envelop the object, entirely disintegrating it."
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Yeah, I'm the owner. I'm also the manager too.
This could be easily pared down to;
"I am the owner and manager.
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How long has Mr. ██████ been working here, and at which position?
I would personally change "at what position?" to "in what capacity?"
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That is all that I found in terms of serious grammar issues, at least of the sort that hinder understanding.