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In my younger days I learned violin. I already had some proficiency reading the treble clef. Took a few years to get good at reading the bass clef. The notes on the staff are arranged in order from the lowest to the highest. You read a C on the staff, the next C would be on the same spot so shouldn't be an issue. The only issue is playing while reading. The first few times when you're not familiar with the notes you hesitate. Once you learned the notes, you'd rely on the sheet to avoid memory slips. Someone like myself used to memorize entire pieces to avoid reading and I still do to some extent. My reading improved a lot over the years.
You should't rely on mneumonics like "Every Good Boy Does Fine" or "All Cow Eat Grass". Thinking about phrases would slow you down. Everybody can recognize the Middle C on the staff. Notes of the staff are arranged in order (line-space-line-space). Needs practice to instantly recognize notes. When notes appear to be in order going up or down you know it's a note run. All you need to read is the first note and you can play other notes after without thinking too much.
You can sign up to the Sight Reading Factory. Practice reading at your own pace. Go through the simple reading exercises and do a playback and see how close you get.
https://www.sightreadingfactory.com/
When it comes pieces for a performance, I'd choose pieces that are repetitive when I have little time to prepare. A few months ago I found an arrangement of Simon Garfunkel "Sound of Silence" with 5 verses. The verses are similar with slight variations between them. The way the piece is arranged with chord arpeggios DFA (D minor) & CEG (C major) are easy to remember. It's a piece I know well so don't need much effort to memorize.