Overall, the sapling appears to be in good shape. The minor amount of leaf yellowing and shedding is typical for birch in our summers, and can be exacerbated by the roots getting too dry, since birch appreciate more evenly-moist soils. When monitoring for watering needs, feel the soil around six inches deep in the tree's root zone, watering well only once it has become somewhat dry to the touch at that depth. Several gallons of water per watering session will likely be needed to thoroughly soak the root zone. How often it will dry enough to need watering will greatly depend on weather and soil type, but as a rough guideline, a moisture-loving plant this size might need checking at least twice a week in hot, rainless weather.

The pale lumps on the foliage are not in focus so we can't quite tell what the symptoms look like, but they resemble galls made by mites, which are very common and occur on a wide variety of trees and shrubs. Despite being a bit of an eyesore, mite galls are not a serious threat to plant health and can be ignored. (Treatment would not remove them at this point anyway.) Raking-up and disposing of the tree's fallen leaves this autumn might reduce mite numbers for next year, but it's not guaranteed, since they can also disperse on the wind, being so tiny.

Miri

Thank you. Attached is another photo of the bugs in case you can see it better. 
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Thank you for the photo. The image is unfortunately not in focus, but what we can see does suggest mite galls, which are not concerning.

Miri

Thank you. Right next to the river birch sapling is witch hazel that has things on its leaves. Are these gall mites too? Should i do anything? 
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The growths on the witchhazel are indeed galls, but caused by a specialized aphid (the Witchhazel Cone Gall Aphid), not mites. The aphid is native and essentially harmless, and uses both witchhazel and, as it happens, river birch as its two host plants that it moves between at different times of year. No intervention is necessary.

Miri

Thank you!
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You're welcome!