Hi @Robert_Baran
And welcome in the community! 
If you can share a sample doc it’s gonna be easier, but anyway,
I think that there are 2 possible approach to this, the first is to use a button to copy the needed row into a new table, where people can check in or out!
The second one is to use just one table for all activities with a “user” column that is gonna be used as a filter to get only the row they are interested in
My best approach would be to use a mixture of both system, i would keep one table with all the activities, those will be associated with some users, and they, just by pressing a button, can copy those row in a second table that is kept as record of the done activities (the button to say “log out” or finish this activity will be in the second table)
So, the first table can be super useful to manage activities that have to be periodically done, to have them in just one spot, when a button named maybe “i will take care of this” will add this row to the second table, changing the “date” to Now() and the “user” to whoever pressed that button.
To say “finish” like ok i’ve done it in the second table there will be a button called “i’ve done it” that change a value in the “finish date” column and this give you total worked hours, that you can then report as you prefer in other parts of the doc!
Said like this maybe it could be a little complicated, but if you share a doc i’ll help you 
Have a nice making!
Mario