In Vega Conflict, time can be reduced on builds, upgrades, refits, research, and crafting by using gold. If an item was accidentally accelerated using gold, it cannot be reversed. 

If a build, upgrade, or refit was cancelled, in most cases you can just start it again. If it is cancelled within the first 5 minutes, you get the resources back. 

The exception to this is Dreadnoughts. With the limit on these, if you cancel a hull or upgrade crafting, the fragments do not get returned to you. These also cannot be earned again. Please contact support for further help.