“Sometimes I'll run into him on the street, and he doesn't even acknowledge that I'm there.”

You're drinking with coworkers after work. You're gossiping about the director of your department. You feel like he doesn't notice you at all, and you give an example of this. You say:

Sometimes I'll run into him on the street, and he doesn't even acknowledge that I'm there.

sometimes I'll (do something)

When you're talking in casual spoken English about things that sometimes happen, you can use the phrase "sometimes I'll ___". For example:

Sometimes I'll go for two or three months without calling or writing to my parents. Other times I'll call them 3 times a week.

Sometimes when I'm watching a really sad movie I'll get really into it and start crying so hard, it's embarrassing.

In addition to "sometimes", you can also say "often times I'll ___" or "I'll always ___".

run into (someone)

This means to meet someone unexpectedly. For example:

I ran into someone I haven't seen in years.

A common place to "run into" someone is "on the street". That means outside in a public place, like on a sidewalk.

acknowledge that (someone) is there

This means to show that you notice someone, by talking to them, smiling at them, or just making eye contact (which is when you both look at each other's eyes).

More generally, to "acknowledge (something)" means to admit it, or to show that you notice and recognize it. For example:

Don't you think that his mother should at least acknowledge me? That's just rude.

The U.N. said it had asked North Korea for a meeting about all of this, but the North Koreans even refused to acknowledge that they had received that request for a meeting.