@SandiNa I would start by putting all contracts in one single structured table. Add one or more columns to designate the origin and perhaps type of contract. Something you now seem to do by creating separate tabs. Some columns may not be applicable for all contracts. Just leave them blank. But then, at least, something like "Expiry date" is in the same column for every contract. And as you mentioned yourself already, tidy up the data. Dates only in date columns, add an extra column for the text comments if needed.
Once all that is done, you can filter out the information you need, e.g. all contacts of a certain type, or all contract that will expire in the next three months, or all contracts that have expired more that 30 days ago.
Depending on your Excel version and platform (PC or Mac) and the magnitude of the data, there are various ways of doing this.
