One month before a heart attack, your feet will warn you of these 6 signs, especially to the 3th

Your sentence needs a few grammar corrections. Here are better versions:

Corrected sentence

“One month before a heart attack, your feet may warn you with these 6 signs—especially the 3rd one.”

What was corrected

• “3th” → “3rd” (correct ordinal form)
• “especially to the 3th” → “especially the 3rd one” (more natural English)

Other natural alternatives

1. “Your feet may show these 6 warning signs one month before a heart attack—especially the 3rd one.”
2. “These 6 signs in your feet could appear one month before a heart attack, especially the third.”
3. “Watch for these 6 foot warning signs that may appear a month before a heart attack—especially the 3rd.”

If you want, I can also help you rewrite it as a catchy YouTube title or headline (which is usually how sentences like this are used).