Fix Excel Formatting & Characters

I have a small batch of Excel workbooks—between four and six in total—that I open in Microsoft 365. Each file shows garbled umlauts and other special symbols, and the internal formatting is inconsistent: dates come through as plain text, numeric columns carry stray apostrophes, and some sheets rely on messy merged cells.

Your task is to make every special character display correctly and bring the formatting into a clean, uniform state so the files import smoothly into our bookkeeping tool. Use whatever technique suits you best—Power Query, VBA, or careful manual cleaning—as long as the finished files behave like normal, standards-compliant .xlsx workbooks.

Deliverables
• A corrected .xlsx version of every original file
• A brief note summarising the main fixes applied in each workbook

I’ll confirm acceptance by opening the returned files in Microsoft 365: all formulas must calculate without conversion prompts, and every ä, ö, ü, and other special character must appear exactly as intended.