The original design looks quite professional, with the exception of a few minor points:
"Celebrating" and "Years" need to be in the same font, and not stretched out of proportion. That, plus fix the margins so they line up better on the 3 lines of text. Also put "Years" on a white background, same as the rest of the speed limit
sign - the reversed black-on-white "band" at the bottom makes the
sign look upside down, as that's almost always done at the top of traffic/safety
signs, and it's not normally done on speed limit
signs at all.