import re
sentence = "open app store and maybe app marker here"
pattern = re.compile(r'\b(app)\s+([a-z])', re.I)
sentence = re.sub(pattern, r'\1\2', sentence)
print(sentence)
aW1wb3J0IHJlCnNlbnRlbmNlID0gIm9wZW4gYXBwIHN0b3JlIGFuZCBtYXliZSBhcHAgbWFya2VyIGhlcmUiCnBhdHRlcm4gPSByZS5jb21waWxlKHInXGIoYXBwKVxzKyhbYS16XSknLCByZS5JKQpzZW50ZW5jZSA9IHJlLnN1YihwYXR0ZXJuLCByJ1wxXDInLCBzZW50ZW5jZSkKcHJpbnQoc2VudGVuY2Up