Search/find window behaviour---spinning wheel

Just merely a beginner, a question to the other users/developers:
I’m facing a drastic speed-dump within the search/find window, entering words for searching. Just moving the cursor (via arrow keys up/down) from, for example, behind the word to the beginning results in half a minute spinning wheel. The same by re-typing or alter some letters.
I’m using a G4 PB (1.33) with 1 GB RAM.
(I forgot: 10.3.4)

BTW 1: the fuzzy search radio button is dimmed — why?
BTW 2: IMO the HELP is not as much a help for this topic — how to search more precisely. (Not as much a help for a non-specialist in <grep> or thelike :wink: Could you give me some more hints in advanced searching/finding?

Thanks for your advice(s)