Welcome to MP! We all started somewhere. There are some advantages to being given a plant and some disadvantages. However, before we discuss that, let's see what we can do to help you get that plant growing as it should be.
First of all, you really need to amend your soil. There are very few (if any) native soils that could not benefit from amendments and most really need amending. Your soil appears dense without good drainage properties. I would encourage you to check out some soil mixtures--it is very important to have the proper soil mixture when growing cannabis. I am thinking that you are going to need to add lime, perlite, compost, worm castings, peat moss, etc. If you are growing organic, you will want to add some other things to the mix.
The next thing to do is get the bug problem (if that mis what it is) taken care of. If an exam shows no insect activity, something else is wrong and we will see what we can do. I have never had thrips, so know nothing about them or how to battle them. Rosebud was the one who told me about SNS products and I really like them.
As Hamster mentioned, the plant looks like it is revegging. See if you can find out more about the life of the plant prior to you getting it--how old is it, was it flowered, partially harvested, and then put back into veg, what strain? I kind of find it strange that someone would give a new grower a revegging plant and not tell them that or how to care for it.
Your next step will be to decide on a nutrient regime for it. I really recommend nutrients formulated for cannabis. Marijuana has different nutrient needs during different phases of its life. Even if you are growing organic, I think it is nice to have some commercial organic nutrients sitting on the shelf.