Is it common to say "joining me today is [someone]"? Isn't is more natural to say "[someone] is joining me today"?

What does "deli" mean?

"Deli" is short for "delicatessen," which are shops where ready-made food is sold. This can include cut meats, sandwiches, salads, and so on. In America and Canada, many of these delis are run by Jewish owners or cater to Jewish clientele, so they are sometimes called "Jewish delis" to indicate the type of food served there.

Why's "for" in the end of the sentence?

The preposition "for" is at the end of the sentence to refer back to the object mentioned in the beginning. It's relating to that object. Specifically referring to the "bought things" here. You can use this with other sentences, too! Sometimes it also means "because of." Ex: How long are you here for? Ex: She's the lady I made this cake for. => referring back to "the lady" Ex: I'm not sure what this is for.

Can I say "I can't see anybody" instead of "I don't see anybody"?

Remember that there is a difference between "don't" and "can't," as "can't" often carries the connotation of not having the ability or skill to do something, whereas "don't" implies that one has the ability or skill to do it but can't for some reason. In this case, nothing is impeding the speaker's sight, but he still does not see anyone. In informal situations like in this video, "can't" is used interchangeably with "don't" to mean the same thing, but the latter is more preferable and accurate. Ex: I can't drive a car as I never learnt how to. (Does not have the ability) Ex: I don't drive a car because I don't have my license expired. (Has the ability, but another reason prevents the doing of something)

What other words can I use instead of "smashed" here?

"Smashed it" is a common British expression that means something was done really well. You can also say "nailed it" or "killed it" which are both a little more informal but common in American English to express the same meaning of doing something really well. Ex: Great job singing, you killed it! Ex: He nailed the interview.

Is there a difference in nuance if I omit 'self-' in this sentence? I think it's better to use 'conscious' or 'aware' when talking about general things like environmental issues.

When "self" is used in combination with another word, it usually indicates that this is an action being done to oneself. For example, a "self-reflection" is a reflection done by a person about themselves. "Self-conscious" is the same thing - it means to be aware (conscious) of oneself. Thus, if someone were to say that they were feeling "self-conscious," it means that they are feeling particularly aware (even nervous!) about themselves and how they might be perceived by others. Ex: I wore an ugly shirt to school and felt self-conscious all day. Ex: I have always had an independent and self-reliant personality.