I believe for the FR60 walkie-talkies, if they are not sending or receiving, the issue could be related to the antenna, battery, or internal components. You can try replacing the batteries and/or antennas to see if that resolves the issue.
As for the T5820 walkie-talkie, if the rubber on the antenna is broken, it's likely that the antenna itself is also damaged. In this case, you can try replacing the antenna with a new one. Antennas are typically available for purchase online or at electronics stores.
In terms of cost, repairing older walkie-talkies like these may not always be cost-effective. If the repairs are extensive or require replacement of major components, it may be more practical to purchase new walkie-talkies instead.
Below are options of the options of walkie-talkies you can buy;